W3C

W3C XML Schema Definition Language (XSD) 1.1 Part 2: Datatypes

W3C Recommendation 5 April 2012

This version:
http://www.w3.org/TR/2012/REC-xmlschema11-2-20120405/
Latest version:
http://www.w3.org/TR/xmlschema11-2/
Previous version:
http://www.w3.org/TR/2012/PR-xmlschema11-2-20120119/
Editors (Version 1.1):
David Peterson, invited expert (SGMLWorks!) <davep@iit.edu>
Shudi (Sandy) Gao 高殊镝, IBM <sandygao@ca.ibm.com>
Ashok Malhotra, Oracle Corporation <ashokmalhotra@alum.mit.edu>
C. M. Sperberg-McQueen, Black Mesa Technologies LLC <cmsmcq@blackmesatech.com>
Henry S. Thompson, University of Edinburgh <ht@inf.ed.ac.uk>
Editors (Version 1.0):
Paul V. Biron, Kaiser Permanente, for Health Level Seven <paul@sparrow-hawk.org>
Ashok Malhotra, Oracle Corporation <ashokmalhotra@alum.mit.edu>

Please refer to the errata for this document, which may include some normative corrections.

See also translations.

This document is also available in these non-normative formats: XML, XHTML with changes since version 1.0 marked, XHTML with changes since previous Working Draft marked, Independent copy of the schema for schema documents, Independent copy of the DTD for schema documents, and List of translations.


Abstract

XML Schema: Datatypes is part 2 of the specification of the XML Schema language. It defines facilities for defining datatypes to be used in XML Schemas as well as other XML specifications. The datatype language, which is itself represented in XML, provides a superset of the capabilities found in XML document type definitions (DTDs) for specifying datatypes on elements and attributes.

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This W3C Recommendation specifies the W3C XML Schema Definition Language (XSD) 1.1 Part 2: Datatypes. It is here made available for review by W3C members and the public.

Changes since the previous public Working Draft include the following:

For those primarily interested in the changes since version 1.0, the appendix Changes since version 1.0 (§I) is the recommended starting point. An accompanying version of this document displays in color all changes to normative text since version 1.0; another shows changes since the previous Working Draft.

Comments on this document should be made in W3C's public installation of Bugzilla, specifying "XML Schema" as the product. Instructions can be found at http://www.w3.org/XML/2006/01/public-bugzilla. If access to Bugzilla is not feasible, please send your comments to the W3C XML Schema comments mailing list, www-xml-schema-comments@w3.org (archive) and note explicitly that you have not made a Bugzilla entry for the comment. Each Bugzilla entry and email message should contain only one comment.

This document has been reviewed by W3C Members, by software developers, and by other W3C groups and interested parties, and is endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited from another document. W3C's role in making the Recommendation is to draw attention to the specification and to promote its widespread deployment. This enhances the functionality and interoperability of the Web.

An implementation report for XSD 1.1 was prepared and used in the Director's decision to publish the previous version of this specification as a Proposed Recommendation. The Director's decision to publish this document as a W3C Recommendation is based on consideration of reviews of the Proposed Recommendation by the public and by the members of the W3C Advisory committee.

The W3C XML Schema Working Group intends to process comments made about this recommendation, with any approved changes being handled as errata to be published separately.

This document has been produced by the W3C XML Schema Working Group as part of the W3C XML Activity. The goals of the XML Schema language version 1.1 are discussed in the Requirements for XML Schema 1.1 document. The authors of this document are the members of the XML Schema Working Group. Different parts of this specification have different editors.

This document was produced by a group operating under the 5 February 2004 W3C Patent Policy. W3C maintains a public list of any patent disclosures made in connection with the deliverables of the group; that page also includes instructions for disclosing a patent. An individual who has actual knowledge of a patent which the individual believes contains Essential Claim(s) must disclose the information in accordance with section 6 of the W3C Patent Policy.

The English version of this specification is the only normative version. Information about translations of this document is available at http://www.w3.org/2003/03/Translations/byTechnology?technology=xmlschema.

Table of Contents

1 Introduction
    1.1 Introduction to Version 1.1
    1.2 Purpose
    1.3 Dependencies on Other Specifications
    1.4 Requirements
    1.5 Scope
    1.6 Terminology
    1.7 Constraints and Contributions
2 Datatype System
    2.1 Datatype
    2.2 Value space
Identity · Equality · Order
    2.3 The Lexical Space and Lexical Mapping
Canonical Mapping
    2.4 Datatype Distinctions
Atomic vs. List vs. Union Datatypes · Special vs. Primitive vs. Ordinary Datatypes · Definition, Derivation, Restriction, and Construction · Built-in vs. User-Defined Datatypes
3 Built-in Datatypes and Their Definitions
    3.1 Namespace considerations
    3.2 Special Built-in Datatypes
anySimpleType · anyAtomicType
    3.3 Primitive Datatypes
string · boolean · decimal · float · double · duration · dateTime · time · date · gYearMonth · gYear · gMonthDay · gDay · gMonth · hexBinary · base64Binary · anyURI · QName · NOTATION
    3.4 Other Built-in Datatypes
normalizedString · token · language · NMTOKEN · NMTOKENS · Name · NCName · ID · IDREF · IDREFS · ENTITY · ENTITIES · integer · nonPositiveInteger · negativeInteger · long · int · short · byte · nonNegativeInteger · unsignedLong · unsignedInt · unsignedShort · unsignedByte · positiveInteger · yearMonthDuration · dayTimeDuration · dateTimeStamp
4 Datatype components
    4.1 Simple Type Definition
The Simple Type Definition Schema Component · XML Representation of Simple Type Definition Schema Components · Constraints on XML Representation of Simple Type Definition · Simple Type Definition Validation Rules · Constraints on Simple Type Definition Schema Components · Built-in Simple Type Definitions
    4.2 Fundamental Facets
ordered · bounded · cardinality · numeric
    4.3 Constraining Facets
length · minLength · maxLength · pattern · enumeration · whiteSpace · maxInclusive · maxExclusive · minExclusive · minInclusive · totalDigits · fractionDigits · Assertions · explicitTimezone
5 Conformance
    5.1 Host Languages
    5.2 Independent implementations
    5.3 Conformance of data
    5.4 Partial Implementation of Infinite Datatypes

Appendices

A Schema for Schema Documents (Datatypes) (normative)
B DTD for Datatype Definitions (non-normative)
C Illustrative XML representations for the built-in simple type definitions
    C.1 Illustrative XML representations for the built-in primitive type definitions
    C.2 Illustrative XML representations for the built-in ordinary type definitions
D Built-up Value Spaces
    D.1 Numerical Values
Exact Lexical Mappings
    D.2 Date/time Values
The Seven-property Model · Lexical Mappings
E Function Definitions
    E.1 Generic Number-related Functions
    E.2 Duration-related Definitions
    E.3 Date/time-related Definitions
Normalization of property values · Auxiliary Functions · Adding durations to dateTimes · Time on timeline · Lexical mappings · Canonical Mappings
    E.4 Lexical and Canonical Mappings for Other Datatypes
Lexical and canonical mappings for
F Datatypes and Facets
    F.1 Fundamental Facets
G Regular Expressions
    G.1 Regular expressions and branches
    G.2 Pieces, atoms, quantifiers
    G.3 Characters and metacharacters
    G.4 Character Classes
Character class expressions · Character Class Escapes
H Implementation-defined and implementation-dependent features (normative)
    H.1 Implementation-defined features
    H.2 Implementation-dependent features
I Changes since version 1.0
    I.1 Datatypes and Facets
    I.2 Numerical Datatypes
    I.3 Date/time Datatypes
    I.4 Other changes
J Glossary (non-normative)
K References
    K.1 Normative
    K.2 Non-normative
L Acknowledgements (non-normative)

1 Introduction

next sub-section1.1 Introduction to Version 1.1

The Working Group has two main goals for this version of W3C XML Schema:

  • Significant improvements in simplicity of design and clarity of exposition without loss of backward or forward compatibility;
  • Provision of support for versioning of XML languages defined using the XML Schema specification, including the XML transfer syntax for schemas itself.

These goals are slightly in tension with one another -- the following summarizes the Working Group's strategic guidelines for changes between versions 1.0 and 1.1:

  1. Add support for versioning (acknowledging that this may be slightly disruptive to the XML transfer syntax at the margins)
  2. Allow bug fixes (unless in specific cases we decide that the fix is too disruptive for a point release)
  3. Allow editorial changes
  4. Allow design cleanup to change behavior in edge cases
  5. Allow relatively non-disruptive changes to type hierarchy (to better support current and forthcoming international standards and W3C recommendations)
  6. Allow design cleanup to change component structure (changes to functionality restricted to edge cases)
  7. Do not allow any significant changes in functionality
  8. Do not allow any changes to XML transfer syntax except those required by version control hooks and bug fixes

The overall aim as regards compatibility is that

  • All schema documents conformant to version 1.0 of this specification should also conform to version 1.1, and should have the same validation behavior across 1.0 and 1.1 implementations (except possibly in edge cases and in the details of the resulting PSVI);
  • The vast majority of schema documents conformant to version 1.1 of this specification should also conform to version 1.0, leaving aside any incompatibilities arising from support for versioning, and when they are conformant to version 1.0 (or are made conformant by the removal of versioning information), should have the same validation behavior across 1.0 and 1.1 implementations (again except possibly in edge cases and in the details of the resulting PSVI);

previous sub-section next sub-section1.2 Purpose

The [XML] specification defines limited facilities for applying datatypes to document content in that documents may contain or refer to DTDs that assign types to elements and attributes. However, document authors, including authors of traditional documents and those transporting data in XML, often require a higher degree of type checking to ensure robustness in document understanding and data interchange.

The table below offers two typical examples of XML instances in which datatypes are implicit: the instance on the left represents a billing invoice, the instance on the right a memo or perhaps an email message in XML.

Data orientedDocument oriented
<invoice>
  <orderDate>1999-01-21</orderDate>
  <shipDate>1999-01-25</shipDate>
  <billingAddress>
   <name>Ashok Malhotra</name>
   <street>123 Microsoft Ave.</street>
   <city>Hawthorne</city>
   <state>NY</state>
   <zip>10532-0000</zip>
  </billingAddress>
  <voice>555-1234</voice>
  <fax>555-4321</fax>
</invoice>
<memo importance='high'
      date='1999-03-23'>
  <from>Paul V. Biron</from>
  <to>Ashok Malhotra</to>
  <subject>Latest draft</subject>
  <body>
    We need to discuss the latest
    draft <emph>immediately</emph>.
    Either email me at <email>
    mailto:paul.v.biron@kp.org</email>
    or call <phone>555-9876</phone>
  </body>
</memo>

The invoice contains several dates and telephone numbers, the postal abbreviation for a state (which comes from an enumerated list of sanctioned values), and a ZIP code (which takes a definable regular form).  The memo contains many of the same types of information: a date, telephone number, email address and an "importance" value (from an enumerated list, such as "low", "medium" or "high").  Applications which process invoices and memos need to raise exceptions if something that was supposed to be a date or telephone number does not conform to the rules for valid dates or telephone numbers.

In both cases, validity constraints exist on the content of the instances that are not expressible in XML DTDs.  The limited datatyping facilities in XML have prevented validating XML processors from supplying the rigorous type checking required in these situations.  The result has been that individual applications writers have had to implement type checking in an ad hoc manner.  This specification addresses the need of both document authors and applications writers for a robust, extensible datatype system for XML which could be incorporated into XML processors.  As discussed below, these datatypes could be used in other XML-related standards as well.

previous sub-section next sub-section1.3 Dependencies on Other Specifications

Other specifications on which this one depends are listed in References (§K).

This specification defines some datatypes which depend on definitions in [XML] and [Namespaces in XML]; those definitions, and therefore the datatypes based on them, vary between version 1.0 ([XML 1.0], [Namespaces in XML 1.0]) and version 1.1 ([XML], [Namespaces in XML]) of those specifications. In any given use of this specification, the choice of the 1.0 or the 1.1 definition of those datatypes is ·implementation-defined·.

Conforming implementations of this specification may provide either the 1.1-based datatypes or the 1.0-based datatypes, or both. If both are supported, the choice of which datatypes to use in a particular assessment episode should be under user control.

Note: When this specification is used to check the datatype validity of XML input, implementations may provide the heuristic of using the 1.1 datatypes if the input is labeled as XML 1.1, and using the 1.0 datatypes if the input is labeled 1.0, but this heuristic should be subject to override by users, to support cases where users wish to accept XML 1.1 input but validate it using the 1.0 datatypes, or accept XML 1.0 input and validate it using the 1.1 datatypes.

This specification makes use of the EBNF notation used in the [XML] specification. Note that some constructs of the EBNF notation used here resemble the regular-expression syntax defined in this specification (Regular Expressions (§G)), but that they are not identical: there are differences. For a fuller description of the EBNF notation, see Section 6. Notation of the [XML] specification.

previous sub-section next sub-section1.4 Requirements

The [XML Schema Requirements] document spells out concrete requirements to be fulfilled by this specification, which state that the XML Schema Language must:

  1. provide for primitive data typing, including byte, date, integer, sequence, SQL and Java primitive datatypes, etc.;
  2. define a type system that is adequate for import/export from database systems (e.g., relational, object, OLAP);
  3. distinguish requirements relating to lexical data representation vs. those governing an underlying information set;
  4. allow creation of user-defined datatypes, such as datatypes that are derived from existing datatypes and which may constrain certain of its properties (e.g., range, precision, length, format).

previous sub-section next sub-section1.5 Scope

This specification defines datatypes that can be used in an XML Schema.  These datatypes can be specified for element content that would be specified as #PCDATA and attribute values of various types in a DTD.  It is the intention of this specification that it be usable outside of the context of XML Schemas for a wide range of other XML-related activities such as [XSL] and [RDF Schema].

previous sub-section next sub-section1.6 Terminology

The terminology used to describe XML Schema Datatypes is defined in the body of this specification. The terms defined in the following list are used in building those definitions and in describing the actions of a datatype processor:

[Definition:]  for compatibility
A feature of this specification included solely to ensure that schemas which use this feature remain compatible with [XML].
(Of strings or names:) Two strings or names being compared must be identical. Characters with multiple possible representations in ISO/IEC 10646 (e.g. characters with both precomposed and base+diacritic forms) match only if they have the same representation in both strings. No case folding is performed.
(Of strings and rules in the grammar:) A string matches a grammatical production if and only if it belongs to the language generated by that production.
Schemas, schema documents, and processors are permitted to but need not behave as described.
It is recommended that schemas, schema documents, and processors behave as described, but there can be valid reasons for them not to; it is important that the full implications be understood and carefully weighed before adopting behavior at variance with the recommendation.
(Of schemas and schema documents:) Schemas and documents are required to behave as described; otherwise they are in ·error·.
(Of processors:) Processors are required to behave as described.
Schemas, schema documents and processors are forbidden to behave as described; schemas and documents which nevertheless do so are in ·error·.
A failure of a schema or schema document to conform to the rules of this specification.
Except as otherwise specified, processors must distinguish error-free (conforming) schemas and schema documents from those with errors; if a schema used in type-validation or a schema document used in constructing a schema is in error, processors must report the fact; if more than one is in error, it is ·implementation-dependent· whether more than one is reported as being in error. If more than one of the constraints given in this specification is violated, it is ·implementation-dependent· how many of the violations, and which, are reported.
Note: Failure of an XML element or attribute to be datatype-valid against a particular datatype in a particular schema is not in itself a failure to conform to this specification and thus, for purposes of this specification, not an error.
[Definition:]  user option
A choice left under the control of the user of a processor, rather than being fixed for all users or uses of the processor.
Statements in this specification that "Processors may at user option" behave in a certain way mean that processors may provide mechanisms to allow users (i.e. invokers of the processor) to enable or disable the behavior indicated. Processors which do not provide such user-operable controls must not behave in the way indicated. Processors which do provide such user-operable controls must make it possible for the user to disable the optional behavior.
Note: The normal expectation is that the default setting for such options will be to disable the optional behavior in question, enabling it only when the user explicitly requests it. This is not, however, a requirement of conformance: if the processor's documentation makes clear that the user can disable the optional behavior, then invoking the processor without requesting that it be disabled can be taken as equivalent to a request that it be enabled. It is required, however, that it in fact be possible for the user to disable the optional behavior.
Note: Nothing in this specification constrains the manner in which processors allow users to control user options. Command-line options, menu choices in a graphical user interface, environment variables, alternative call patterns in an application programming interface, and other mechanisms may all be taken as providing user options.

previous sub-section 1.7 Constraints and Contributions

This specification provides three different kinds of normative statements about schema components, their representations in XML and their contribution to the schema-validation of information items:

[Definition:]   Constraint on Schemas
Constraints on the schema components themselves, i.e. conditions components must satisfy to be components at all. Largely to be found in Datatype components (§4).
[Definition:]   Schema Representation Constraint
Constraints on the representation of schema components in XML.  Some but not all of these are expressed in Schema for Schema Documents (Datatypes) (normative) (§A) and DTD for Datatype Definitions (non-normative) (§B).
[Definition:]   Validation Rule
Constraints expressed by schema components which information items must satisfy to be schema-valid.  Largely to be found in Datatype components (§4).

2 Datatype System

This section describes the conceptual framework behind the datatype system defined in this specification.  The framework has been influenced by the [ISO 11404] standard on language-independent datatypes as well as the datatypes for [SQL] and for programming languages such as Java.

The datatypes discussed in this specification are for the most part well known abstract concepts such as integer and date. It is not the place of this specification to thoroughly define these abstract concepts; many other publications provide excellent definitions. However, this specification will attempt to describe the abstract concepts well enough that they can be readily recognized and distinguished from other abstractions with which they may be confused.

Note: Only those operations and relations needed for schema processing are defined in this specification. Applications using these datatypes are generally expected to implement appropriate additional functions and/or relations to make the datatype generally useful.  For example, the description herein of the float datatype does not define addition or multiplication, much less all of the operations defined for that datatype in [IEEE 754-2008] on which it is based.  For some datatypes (e.g. language or anyURI) defined in part by reference to other specifications which impose constraints not part of the datatypes as defined here, applications may also wish to check that values conform to the requirements given in the current version of the relevant external specification.

next sub-section2.1 Datatype

[Definition:]  In this specification, a datatype has three properties:
Note: This specification only defines the operations and relations needed for schema processing.  The choice of terminology for describing/naming the datatypes is selected to guide users and implementers in how to expand the datatype to be generally useful—i.e., how to recognize the "real world" datatypes and their variants for which the datatypes defined herein are meant to be used for data interchange.

Along with the ·lexical mapping· it is often useful to have an inverse which provides a standard ·lexical representation· for each value.  Such a ·canonical mapping· is not required for schema processing, but is described herein for the benefit of users of this specification, and other specifications which might find it useful to reference these descriptions normatively. For some datatypes, notably QName and NOTATION, the mapping from lexical representations to values is context-dependent; for these types, no ·canonical mapping· is defined.

Note: Where ·canonical mappings· are defined in this specification, they are defined for ·primitive· datatypes. When a datatype is derived using facets which directly constrain the ·value space·, then for each value eliminated from the ·value space·, the corresponding lexical representations are dropped from the lexical space. The ·canonical mapping· for such a datatype is a subset of the ·canonical mapping· for its ·primitive· type and provides a ·canonical representation· for each value remaining in the ·value space·.
The ·pattern· facet, on the other hand, and any other (·implementation-defined·) ·lexical· facets, restrict the ·lexical space· directly. When more than one lexical representation is provided for a given value, such facets may remove the ·canonical representation· while permitting a different lexical representation; in this case, the value remains in the ·value space· but has no ·canonical representation·. This specification provides no recourse in such situations. Applications are free to deal with it as they see fit.
Note: This specification sometimes uses the shorter form "type" where one might strictly speaking expect the longer form "datatype" (e.g. in the phrases "union type", "list type", "base type", "item type", etc. No systematic distinction is intended between the forms of these phrase with "type" and those with "datatype"; the two forms are used interchangeably.
The distinction between "datatype" and "simple type definition", by contrast, carries more information: the datatype is characterized by its ·value space·, ·lexical space·, ·lexical mapping·, etc., as just described, independently of the specific facets or other definitional mechanisms used in the simple type definition to describe that particular ·value space· or ·lexical space·. Different simple type definitions with different selections of facets can describe the same datatype.

previous sub-section next sub-section2.2 Value space

        2.2.1 Identity
        2.2.2 Equality
        2.2.3 Order

[Definition:]  The value space of a datatype is the set of values for that datatype.  Associated with each value space are selected operations and relations necessary to permit proper schema processing.  Each value in the value space of a ·primitive· or ·ordinary· datatype is denoted by one or more character strings in its ·lexical space·, according to ·the lexical mapping·; ·special· datatypes, by contrast, may include "ineffable" values not mapped to by any lexical representation. (If the mapping is restricted during a derivation in such a way that a value has no denotation, that value is dropped from the value space.)

The value spaces of datatypes are abstractions, and are defined in Built-in Datatypes and Their Definitions (§3) to the extent needed to clarify them for readers.  For example, in defining the numerical datatypes, we assume some general numerical concepts such as number and integer are known.  In many cases we provide references to other documents providing more complete definitions.

Note: The value spaces and the values therein are abstractions.  This specification does not prescribe any particular internal representations that must be used when implementing these datatypes.  In some cases, there are references to other specifications which do prescribe specific internal representations; these specific internal representations must be used to comply with those other specifications, but need not be used to comply with this specification.
In addition, other applications are expected to define additional appropriate operations and/or relations on these value spaces (e.g., addition and multiplication on the various numerical datatypes' value spaces), and are permitted where appropriate to even redefine the operations and relations defined within this specification, provided that for schema processing the relations and operations used are those defined herein.
The ·value space· of a datatype can be defined in one of the following ways:
  • defined elsewhere axiomatically from fundamental notions (intensional definition) [see ·primitive·]
  • enumerated outright from values of an already defined datatype (extensional definition) [see ·enumeration·]
  • defined by restricting the ·value space· of an already defined datatype to a particular subset with a given set of properties [see ·derived·]
  • defined as a combination of values from one or more already defined ·value space·(s) by a specific construction procedure [see ·list· and ·union·]

The relations of identity and equality are required for each value space. An order relation is specified for some value spaces, but not all. A very few datatypes have other relations or operations prescribed for the purposes of this specification.

2.2.1 Identity

The identity relation is always defined. Every value space inherently has an identity relation. Two things are identical if and only if they are actually the same thing: i.e., if there is no way whatever to tell them apart. 

Note: This does not preclude implementing datatypes by using more than one internal representation for a given value, provided no mechanism inherent in the datatype implementation (i.e., other than bit-string-preserving "casting" of the datum to a different datatype) will distinguish between the two representations.

In the identity relation defined herein, values from different ·primitive· datatypes' ·value spaces· are made artificially distinct if they might otherwise be considered identical.  For example, there is a number two in the decimal datatype and a number two in the float datatype.  In the identity relation defined herein, these two values are considered distinct.  Other applications making use of these datatypes may choose to consider values such as these identical, but for the view of ·primitive· datatypes' ·value spaces· used herein, they are distinct.

WARNING:  Care must be taken when identifying values across distinct primitive datatypes.  The ·literals· '0.1' and '0.10000000009' map to the same value in float (neither 0.1 nor 0.10000000009 is in the value space, and each literal is mapped to the nearest value, namely 0.100000001490116119384765625), but map to distinct values in decimal.

Note: Datatypes ·constructed· by ·facet-based restriction· do not create new values; they define subsets of some ·primitive· datatype's ·value space·. A consequence of this fact is that the ·literals· '+2', treated as a decimal, '+2', treated as an integer, and '+2', treated as a byte, all denote the same value. They are not only equal but identical.

Given a list A and a list B, A and B are the same list if they are the same sequence of atomic values. The necessary and sufficient conditions for this identity are that A and B have the same length and that the items of A are pairwise identical to the items of B.

Note: It is a consequence of the rule just given for list identity that there is only one empty list. An empty list declared as having ·item type· decimal and an empty list declared as having ·item type· string are not only equal but identical.

2.2.2 Equality

Each ·primitive· datatype has prescribed an equality relation for its value space.  The equality relation for most datatypes is the identity relation.  In the few cases where it is not, equality has been carefully defined so that for most operations of interest to the datatype, if two values are equal and one is substituted for the other as an argument to any of the operations, the results will always also be equal.

On the other hand, equality need not cover the entire value space of the datatype (though it usually does). In particular, NaN is not equal to itself in the float and double datatypes.

This equality relation is used in conjunction with identity when making ·facet-based restrictions· by enumeration, when checking identity constraints (in the context of [XSD 1.1 Part 1: Structures]) and when checking value constraints. It is used in conjunction with order when making ·facet-based restrictions· involving order. The equality relation used in the evaluation of XPath expressions may differ.  When processing XPath expressions as part of XML schema-validity assessment or otherwise testing membership in the ·value space· of a datatype whose derivation involves ·assertions·, equality (like all other relations) within those expressions is interpreted using the rules of XPath ([XPath 2.0]).  All comparisons for "sameness" prescribed by this specification test for either equality or identity, not for identity alone.

Note: In the prior version of this specification (1.0), equality was always identity.  This has been changed to permit the datatypes defined herein to more closely match the "real world" datatypes for which they are intended to be used as transmission formats.
For example, the float datatype has an equality which is not the identity ( −0 = +0 , but they are not identical—although they were identical in the 1.0 version of this specification), and whose domain excludes one value, NaN, so that  NaN ≠ NaN .
For another example, the dateTime datatype previously lost any time-zone offset information in the ·lexical representation· as the value was converted to ·UTC·; now the time zone offset is retained and two values representing the same "moment in time" but with different remembered time zone offsets are now equal but not identical.

In the equality relation defined herein, values from different primitive data spaces are made artificially unequal even if they might otherwise be considered equal.  For example, there is a number two in the decimal datatype and a number two in the float datatype.  In the equality relation defined herein, these two values are considered unequal.  Other applications making use of these datatypes may choose to consider values such as these equal; nonetheless, in the equality relation defined herein, they are unequal.

Two lists A and B are equal if and only if they have the same length and their items are pairwise equal. A list of length one containing a value V1 and an atomic value V2 are equal if and only if V1 is equal to V2.

For the purposes of this specification, there is one equality relation for all values of all datatypes (the union of the various datatype's individual equalities, if one consider relations to be sets of ordered pairs).  The equality relation is denoted by '=' and its negation by '≠', each used as a binary infix predicate:  x = y  and  x ≠ y .  On the other hand, identity relationships are always described in words.

2.2.3 Order

For some datatypes, an order relation is prescribed for use in checking upper and lower bounds of the ·value space·.  This order may be a partial order, which means that there may be values in the ·value space· which are neither equal, less-than, nor greater-than.  Such value pairs are incomparable.  In many cases, no order is prescribed; each pair of values is either equal or ·incomparable·. [Definition:]  Two values that are neither equal, less-than, nor greater-than are incomparable. Two values that are not ·incomparable· are comparable.

The order relation is used in conjunction with equality when making ·facet-based restrictions· involving order.  This is the only use of this order relation for schema processing.  Of course, when processing XPath expressions as part of XML schema-validity assessment or otherwise testing membership in the ·value space· of a datatype whose derivation involves ·assertions·, order (like all other relations) within those expressions is interpreted using the rules of XPath ([XPath 2.0]).

In this specification, this less-than order relation is denoted by '<' (and its inverse by '>'), the weak order by '≤' (and its inverse by '≥'), and the resulting ·incomparable· relation by '<>', each used as a binary infix predicate:  x < y ,  x ≤ y ,  x > y ,  x ≥ y , and  x <> y .

Note: The weak order "less-than-or-equal" means "less-than" or "equal" and one can tell which.  For example, the duration P1M (one month) is not less-than-or-equal P31D (thirty-one days) because P1M is not less than P31D, nor is P1M equal to P31D.  Instead, P1M is ·incomparable· with P31D.)  The formal definition of order for duration (duration (§3.3.6)) ensures that this is true.

For purposes of this specification, the value spaces of primitive datatypes are disjoint, even in cases where the abstractions they represent might be thought of as having values in common.  In the order relations defined in this specification, values from different value spaces are ·incomparable·.  For example, the numbers two and three are values in both the decimal datatype and the float datatype.  In the order relation defined here, the two in the decimal datatype is not less than the three in the float datatype; the two values are incomparable.  Other applications making use of these datatypes may choose to consider values such as these comparable.

Note: Comparison of values from different ·primitive· datatypes can sometimes be an error and sometimes not, depending on context.
When made for purposes of checking an enumeration constraint, such a comparison is not in itself an error, but since no two values from different ·primitive· ·value spaces· are equal, any comparison of ·incomparable· values will invariably be false.
Specifying an upper or lower bound which is of the wrong primitive datatype (and therefore ·incomparable· with the values of the datatype it is supposed to restrict) is, by contrast, always an error. It is a consequence of the rules for ·facet-based restriction· that in conforming simple type definitions, the values of upper and lower bounds, and enumerated values, must be drawn from the value space of the ·base type·, which necessarily means from the same ·primitive· datatype.
Comparison of ·incomparable· values in the context of an XPath expression (e.g. in an assertion or in the rules for conditional type assignment) can raise a dynamic error in the evaluation of the XPath expression; see [XQuery 1.0 and XPath 2.0 Functions and Operators] for details.

previous sub-section next sub-section2.3 The Lexical Space and Lexical Mapping

[Definition:]  The lexical mapping for a datatype is a prescribed relation which maps from the ·lexical space· of the datatype into its ·value space·.

[Definition:]  The lexical space of a datatype is the prescribed set of strings which ·the lexical mapping· for that datatype maps to values of that datatype.

[Definition:]  The members of the ·lexical space· are lexical representations of the values to which they are mapped.

Note: For the ·special· datatypes, the ·lexical mappings· defined here map from the ·lexical space· into, but not onto, the ·value space·. The ·value spaces· of the ·special· datatypes include "ineffable" values for which the ·lexical mappings· defined in this specification provide no lexical representation.
For the ·primitive· and ·ordinary· atomic datatypes, the ·lexical mapping· is a (total) function on the entire ·lexical space· onto (not merely into) the ·value space·: every member of the ·lexical space· maps into the ·value space·, and every value is mapped to by some member of the ·lexical space·.
For ·union· datatypes, the ·lexical mapping· is not necessarily a function, since the same ·literal· may map to different values in different member types. For ·list· datatypes, the ·lexical mapping· is a function if and only if the ·lexical mapping· of the list's ·item type· is a function.

[Definition:]  A sequence of zero or more characters in the Universal Character Set (UCS) which may or may not prove upon inspection to be a member of the ·lexical space· of a given datatype and thus a ·lexical representation· of a given value in that datatype's ·value space·, is referred to as a literal. The term is used indifferently both for character sequences which are members of a particular ·lexical space· and for those which are not.

If a derivation introduces a ·pre-lexical· facet value (a new value for whiteSpace or an implementation-defined ·pre-lexical· facet), the corresponding ·pre-lexical· transformation of a character string, if indeed it changed that string, could prevent that string from ever having the ·lexical mapping· of the derived datatype applied to it.  Character strings that a ·pre-lexical· transformation blocks in this way (i.e., they are not in the range of the ·pre-lexical· facet's transformation) are always dropped from the derived datatype's ·lexical space·.

Note: One should be aware that in the context of XML schema-validity assessment, there are ·pre-lexical· transformations of the input character string (controlled by the whiteSpace facet and any implementation-defined ·pre-lexical· facets) which result in the intended ·literal·.  Systems other than XML schema-validity assessment utilizing this specification may or may not implement these transformations.  If they do not, then input character strings that would have been transformed into correct ·lexical representations·, when taken "raw", may not be correct ·lexical representations·.

Should a derivation be made using a derivation mechanism that removes ·lexical representations· from the·lexical space· to the extent that one or more values cease to have any ·lexical representation·, then those values are dropped from the ·value space·.

Note: This could happen by means of a pattern or other ·lexical· facet, or by a ·pre-lexical· facet as described above.

Conversely, should a derivation remove values then their ·lexical representations· are dropped from the ·lexical space· unless there is a facet value whose impact is defined to cause the otherwise-dropped ·lexical representation· to be mapped to another value instead.

Note: There are currently no facets with such an impact.  There may be in the future.

For example, '100' and '1.0E2' are two different ·lexical representations· from the float datatype which both denote the same value.  The datatype system defined in this specification provides mechanisms for schema designers to control the ·value space· and the corresponding set of acceptable ·lexical representations· of those values for a datatype.

2.3.1 Canonical Mapping

While the datatypes defined in this specification often have a single ·lexical representation· for each value (i.e., each value in the datatype's ·value space· is denoted by a single ·representation· in its ·lexical space·), this is not always the case.  The example in the previous section shows two ·lexical representations· from the float datatype which denote the same value.

[Definition:]  The canonical mapping is a prescribed subset of the inverse of a ·lexical mapping· which is one-to-one and whose domain (where possible) is the entire range of the ·lexical mapping· (the ·value space·).  Thus a ·canonical mapping· selects one ·lexical representation· for each value in the ·value space·.

[Definition:]  The canonical representation of a value in the ·value space· of a datatype is the ·lexical representation· associated with that value by the datatype's ·canonical mapping·.

·Canonical mappings· are not available for datatypes whose ·lexical mappings· are context dependent (i.e., mappings for which the value of a ·lexical representation· depends on the context in which it occurs, or for which a character string may or may not be a valid ·lexical representation· similarly depending on its context)

Note: ·Canonical representations· are provided where feasible for the use of other applications; they are not required for schema processing itself.  A conforming schema processor implementation is not required to implement ·canonical mappings·.

previous sub-section 2.4 Datatype Distinctions

        2.4.1 Atomic vs. List vs. Union Datatypes
            2.4.1.1 Atomic Datatypes
            2.4.1.2 List Datatypes
            2.4.1.3 Union datatypes
        2.4.2 Special vs. Primitive vs. Ordinary Datatypes
            2.4.2.1 Facet-based Restriction
            2.4.2.2 Construction by List
            2.4.2.3 Construction by Union
        2.4.3 Definition, Derivation, Restriction, and Construction
        2.4.4 Built-in vs. User-Defined Datatypes

It is useful to categorize the datatypes defined in this specification along various dimensions, defining terms which can be used to characterize datatypes and the Simple Type Definitions which define them.

2.4.1 Atomic vs. List vs. Union Datatypes

First, we distinguish ·atomic·, ·list·, and ·union· datatypes.

[Definition:]  An atomic value is an elementary value, not constructed from simpler values by any user-accessible means defined by this specification.

For example, a single token which ·matches· Nmtoken from [XML] is in the value space of the ·atomic· datatype NMTOKEN, while a sequence of such tokens is in the value space of the ·list· datatype NMTOKENS.

2.4.1.1 Atomic Datatypes

An ·atomic· datatype has a ·value space· consisting of a set of "atomic" or elementary values.

Note: Atomic values are sometimes regarded, and described, as "not decomposable", but in fact the values in several datatypes defined here are described with internal structure, which is appealed to in checking whether particular values satisfy various constraints (e.g. upper and lower bounds on a datatype). Other specifications which use the datatypes defined here may define operations which attribute internal structure to values and expose or act upon that structure.

The ·lexical space· of an ·atomic· datatype is a set of ·literals· whose internal structure is specific to the datatype in question.

There is one ·special· ·atomic· datatype (anyAtomicType), and a number of ·primitive· ·atomic· datatypes which have anyAtomicType as their ·base type·.  All other ·atomic· datatypes are ·derived· either from one of the ·primitive· ·atomic· datatypes or from another ·ordinary· ·atomic· datatype.  No ·user-defined· datatype may have anyAtomicType as its ·base type·.

2.4.1.2 List Datatypes

·List· datatypes are always ·constructed· from some other type; they are never ·primitive·. The ·value space· of a ·list· datatype is the set of finite-length sequences of zero or more ·atomic· values where each ·atomic· value is drawn from the ·value space· of the lists's ·item type· and has a ·lexical representation· containing no whitespace. The ·lexical space· of a ·list· datatype is a set of ·literals· each of which is a space-separated sequence of ·literals· of the ·item type·.

[Definition:]   The ·atomic· or ·union· datatype that participates in the definition of a ·list· datatype is the item type of that ·list· datatype.  If the ·item type· is a ·union·, each of its ·basic members· must be ·atomic·.

Example
<simpleType name='sizes'>
  <list itemType='decimal'/>
</simpleType>
<cerealSizes xsi:type='sizes'> 8 10.5 12 </cerealSizes>

A ·list· datatype can be ·constructed· from an ordinary or ·primitive· ·atomic· datatype whose ·lexical space· allows whitespace (such as string or anyURI) or a ·union· datatype any of whose {member type definitions}'s ·lexical space· allows space. Since ·list· items are separated at whitespace before the ·lexical representations· of the items are mapped to values, no whitespace will ever occur in the ·lexical representation· of a ·list· item, even when the item type would in principle allow it.  For the same reason, when every possible ·lexical representation· of a given value in the ·value space· of the ·item type· includes whitespace, that value can never occur as an item in any value of the ·list· datatype.

Example
<simpleType name='listOfString'>
  <list itemType='string'/>
</simpleType>
<someElement xsi:type='listOfString'>
this is not list item 1
this is not list item 2
this is not list item 3
</someElement>
In the above example, the value of the someElement element is not a ·list· of ·length· 3; rather, it is a ·list· of ·length· 18.

For each of ·length·, ·maxLength· and ·minLength·, the length is measured in number of list items.  The value of ·whiteSpace· is fixed to the value collapse.

For ·list· datatypes the ·lexical space· is composed of space-separated ·literals· of the ·item type·.  Any ·pattern· specified when a new datatype is ·derived· from a ·list· datatype applies to the members of the ·list· datatype's ·lexical space·, not to the members of the ·lexical space· of the ·item type·.  Similarly, enumerated values are compared to the entire ·list·, not to individual list items, and assertions apply to the entire ·list· too. Lists are identical if and only if they have the same length and their items are pairwise identical; they are equal if and only if they have the same length and their items are pairwise equal. And a list of length one whose item is an atomic value V1 is equal or identical to an atomic value V2 if and only if V1 is equal or identical to V2.

Example
<xs:simpleType name='myList'>
	<xs:list itemType='xs:integer'/>
</xs:simpleType>
<xs:simpleType name='myRestrictedList'>
	<xs:restriction base='myList'>
		<xs:pattern value='123 (\d+\s)*456'/>
	</xs:restriction>
</xs:simpleType>
<someElement xsi:type='myRestrictedList'>123 456</someElement>
<someElement xsi:type='myRestrictedList'>123 987 456</someElement>
<someElement xsi:type='myRestrictedList'>123 987 567 456</someElement>

The ·canonical mapping· of a ·list· datatype maps each value onto the space-separated concatenation of the ·canonical representations· of all the items in the value (in order), using the ·canonical mapping· of the ·item type·.

2.4.1.3 Union datatypes

Union types may be defined in either of two ways. When a union type is ·constructed· by ·union·, its ·value space·, ·lexical space·, and ·lexical mapping· are the "ordered unions" of the ·value spaces·, ·lexical spaces·, and ·lexical mappings· of its ·member types·.

It will be observed that the ·lexical mapping· of a union, so defined, is not necessarily a function: a given ·literal· may map to one value or to several values of different ·primitive· datatypes, and it may be indeterminate which value is to be preferred in a particular context. When the datatypes defined here are used in the context of [XSD 1.1 Part 1: Structures], the xsi:type attribute defined by that specification in section xsi:type can be used to indicate which value a ·literal· which is the content of an element should map to. In other contexts, other rules (such as type coercion rules) may be employed to determine which value is to be used.

When a union type is defined by ·restricting· another ·union·, its ·value space·, ·lexical space·, and ·lexical mapping· are subsets of the ·value spaces·, ·lexical spaces·, and ·lexical mappings· of its ·base type·.

·Union· datatypes are always ·constructed· from other datatypes; they are never ·primitive·. Currently, there are no ·built-in· ·union· datatypes.

Example
A prototypical example of a ·union· type is the maxOccurs attribute on the element element in XML Schema itself: it is a union of nonNegativeInteger and an enumeration with the single member, the string "unbounded", as shown below.
  <attributeGroup name="occurs">
    <attribute name="minOccurs" type="nonNegativeInteger"
    	use="optional" default="1"/>
    <attribute name="maxOccurs"use="optional" default="1">
      <simpleType>
        <union>
          <simpleType>
            <restriction base='nonNegativeInteger'/>
          </simpleType>
          <simpleType>
            <restriction base='string'>
              <enumeration value='unbounded'/>
            </restriction>
          </simpleType>
        </union>
      </simpleType>
    </attribute>
  </attributeGroup>

Any number (zero or more) of ordinary or ·primitive· ·datatypes· can participate in a ·union· type.

[Definition:]   The datatypes that participate in the definition of a ·union· datatype are known as the member types of that ·union· datatype.

Note: When datatypes are represented using XSD schema components, as described in Datatype components (§4), the member types of a union are those simple type definitions given in the {member type definitions} property.

[Definition:]  The transitive membership of a ·union· is the set of its own ·member types·, and the ·member types· of its members, and so on. More formally, if U is a ·union·, then (a) its ·member types· are in the transitive membership of U, and (b) for any datatypes T1 and T2, if T1 is in the transitive membership of U and T2 is one of the ·member types· of T1, then T2 is also in the transitive membership of U.

The ·transitive membership· of a ·union· must not contain the ·union· itself, nor any datatype ·derived· or ·constructed· from the ·union·.

[Definition:]  Those members of the ·transitive membership· of a ·union· datatype U which are themselves not ·union· datatypes are the basic members of U.

[Definition:]  If a datatype M is in the ·transitive membership· of a ·union· datatype U, but not one of U's ·member types·, then a sequence of one or more ·union· datatypes necessarily exists, such that the first is one of the ·member types· of U, each is one of the ·member types· of its predecessor in the sequence, and M is one of the ·member types· of the last in the sequence. The ·union· datatypes in this sequence are said to intervene between M and U. When U and M are given by the context, the datatypes in the sequence are referred to as the intervening unions. When M is one of the ·member types· of U, the set of intervening unions is the empty set.

[Definition:]  In a valid instance of any ·union·, the first of its members in order which accepts the instance as valid is the active member type. [Definition:]  If the ·active member type· is itself a ·union·, one of its members will be its ·active member type·, and so on, until finally a ·basic (non-union) member· is reached. That ·basic member· is the active basic member of the union.

The order in which the ·member types· are specified in the definition (that is, in the case of datatypes defined in a schema document, the order of the <simpleType> children of the <union> element, or the order of the QNames in the memberTypes attribute) is significant. During validation, an element or attribute's value is validated against the ·member types· in the order in which they appear in the definition until a match is found.  As noted above, the evaluation order can be overridden with the use of xsi:type.

Example
For example, given the definition below, the first instance of the <size> element validates correctly as an integer (§3.4.13), the second and third as string (§3.3.1).
  <xs:element name='size'>
    <xs:simpleType>
      <xs:union>
        <xs:simpleType>
          <xs:restriction base='integer'/>
        </xs:simpleType>
        <xs:simpleType>
          <xs:restriction base='string'/>
        </xs:simpleType>
      </xs:union>
    </xs:simpleType>
  </xs:element>
  <size>1</size>
  <size>large</size>
  <size xsi:type='xs:string'>1</size>

The ·canonical mapping· of a ·union· datatype maps each value onto the ·canonical representation· of that value obtained using the ·canonical mapping· of the first ·member type· in whose value space it lies.

2.4.2 Special vs. Primitive vs. Ordinary Datatypes

Next, we distinguish ·special·, ·primitive·, and ·ordinary· (or ·constructed·) datatypes.  Each datatype defined by or in accordance with this specification falls into exactly one of these categories.

For example, in this specification, float is a ·primitive· datatype based on a well-defined mathematical concept and not defined in terms of other datatypes, while integer is ·constructed· from the more general datatype decimal.

2.4.2.1 Facet-based Restriction

[Definition:]  A datatype is defined by facet-based restriction of another datatype (its ·base type·), when values for zero or more ·constraining facets· are specified that serve to constrain its ·value space· and/or its ·lexical space· to a subset of those of the ·base type·. The ·base type· of a ·facet-based restriction· must be a ·primitive· or ·ordinary· datatype.

2.4.2.2 Construction by List

A ·list· datatype can be ·constructed· from another datatype (its ·item type·) by creating a ·value space· that consists of finite-length sequences of zero or more values of its ·item type·. Datatypes so ·constructed· have anySimpleType as their ·base type·. Note that since the ·value space· and ·lexical space· of any ·list· datatype are necessarily subsets of the ·value space· and ·lexical space· of anySimpleType, any datatype ·constructed· as a ·list· is a ·restriction· of its base type.

2.4.2.3 Construction by Union

One datatype can be ·constructed· from one or more datatypes by unioning their ·lexical mappings· and, consequently, their ·value spaces· and ·lexical spaces·.  Datatypes so ·constructed· also have anySimpleType as their ·base type·. Note that since the ·value space· and ·lexical space· of any ·union· datatype are necessarily subsets of the ·value space· and ·lexical space· of anySimpleType, any datatype ·constructed· as a ·union· is a ·restriction· of its base type.

2.4.3 Definition, Derivation, Restriction, and Construction

Definition, derivation, restriction, and construction are conceptually distinct, although in practice they are frequently performed by the same mechanisms.

By 'definition' is meant the explicit identification of the relevant properties of a datatype, in particular its ·value space·, ·lexical space·, and ·lexical mapping·.

The properties of the ·special· and the standard ·primitive· datatypes are defined by this specification. A Simple Type Definition is present for each of these datatypes in every valid schema; it serves as a representation of the datatype, but by itself it does not capture all the relevant information and does not suffice (without knowledge of this specification) to define the datatype.

Note: The properties of any ·implementation-defined· ·primitive· datatypes are given not here but in the documentation for the implementation in question. Alternatively, a primitive datatype not specified in this document can be specified in a document of its own not tied to a particular implementation; [Precision Decimal] is an example of such a document.

For all other datatypes, a Simple Type Definition does suffice. The properties of an ·ordinary· datatype can be inferred from the datatype's Simple Type Definition and the properties of the ·base type·, ·item type· if any, and ·member types· if any. All ·ordinary· datatypes can be defined in this way.

By 'derivation' is meant the relation of a datatype to its ·base type·, or to the ·base type· of its ·base type·, and so on.

Every datatype other than anySimpleType is associated with another datatype, its base type. Base types can be ·special·, ·primitive·, or ·ordinary·.

[Definition:]  A datatype T is immediately derived from another datatype X if and only if X is the ·base type· of T.

Note: The above does not preclude the Simple Type Definition for anySimpleType from having a value for its {base type definition}.  (It does, and its value is anyType.)
More generally,
A datatype R is derived from another datatype B if and only if one of the following is true:

A datatype must not be ·derived· from itself. That is, the base type relation must be acyclic.

It is a consequence of the above that every datatype other than anySimpleType is ·derived· from anySimpleType.

Since each datatype has exactly one ·base type·, and every datatype other than anySimpleType is ·derived· directly or indirectly from anySimpleType, it follows that the ·base type· relation arranges all simple types into a tree structure, which is conventionally referred to as the derivation hierarchy.

By 'restriction' is meant the definition of a datatype whose ·value space· and ·lexical space· are subsets of those of its ·base type·.

Formally, A datatype R is a restriction of another datatype B when

Note that all three forms of datatype ·construction· produce ·restrictions· of the ·base type·: ·facet-based restriction· does so by means of ·constraining facets·, while ·construction· by ·list· or ·union· does so because those ·constructions· take anySimpleType as the ·base type·. It follows that all datatypes are ·restrictions· of anySimpleType. This specification provides no means by which a datatype may be defined so as to have a larger ·lexical space· or ·value space· than its ·base type·.

By 'construction' is meant the creation of a datatype by defining it in terms of another.

[Definition:]  All ·ordinary· datatypes are defined in terms of, or constructed from, other datatypes, either by ·restricting· the ·value space· or ·lexical space· of a ·base type· using zero or more ·constraining facets· or by specifying the new datatype as a ·list· of items of some ·item type·, or by defining it as a ·union· of some specified sequence of ·member types·. These three forms of ·construction· are often called "·facet-based restriction·", "·construction· by ·list·", and "·construction· by ·union·", respectively. Datatypes so constructed may be understood fully (for purposes of a type system) in terms of (a) the properties of the datatype(s) from which they are constructed, and (b) their Simple Type Definition. This distinguishes ·ordinary· datatypes from the ·special· and ·primitive· datatypes, which can be understood only in the light of documentation (namely, their descriptions elsewhere in this specification, or, for ·implementation-defined· ·primitives·, in the appropriate implementation-specific documentation). All ·ordinary· datatypes are ·constructed·, and all ·constructed· datatypes are ·ordinary·.

2.4.4 Built-in vs. User-Defined Datatypes

The ·built-in· datatypes are intended to be available automatically whenever this specification is implemented or used, whether by itself or embedded in a host language. In the language defined by [XSD 1.1 Part 1: Structures], the ·built-in· datatypes are automatically included in every valid schema. Other host languages should specify that all of the datatypes decribed here as built-ins are automatically available; they may specify that additional datatypes are also made available automatically.

Note: ·Implementation-defined· datatypes, whether ·primitive· or ·ordinary·, may sometimes be included automatically in any schemas processed by that implementation; nevertheless, they are not built in to every schema, and are thus not included in the term 'built-in', as that term is used in this specification.

The mechanism for making ·user-defined· datatypes available for use is not defined in this specification; if ·user-defined· datatypes are to be available, some such mechanism must be specified by the host language.

[Definition:]  A datatype which is not available for use is said to be unknown.

Note: From the schema author's perspective, a reference to a datatype which proves to be ·unknown· might reflect any of the following causes, or others:
1 An error has been made in giving the name of the datatype.
2 The datatype is a ·user-defined· datatype which has not been made available using the means defined by the host language (e.g. because the appropriate schema document has not been consulted).
3 The datatype is an ·implementation-defined· ·primitive· datatype not supported by the implementation being used.
4 The datatype is an ·implementation-defined· ·ordinary· datatype which is made automatically available by some implementations, but not by the implementation being used.
5 The datatype is a ·user-defined· ·ordinary· datatype whose base type is ·unknown·
From the point of view of the implementation, these cases are likely to be indistinguishable.
Note: In the terminology of [XSD 1.1 Part 1: Structures], the datatypes here called ·unknown· are referred to as absent.

Conceptually there is no difference between the ·ordinary· ·built-in· datatypes included in this specification and the ·user-defined· datatypes which will be created by individual schema designers. The ·built-in· ·constructed· datatypes are those which are believed to be so common that if they were not defined in this specification many schema designers would end up reinventing them.  Furthermore, including these ·constructed· datatypes in this specification serves to demonstrate the mechanics and utility of the datatype generation facilities of this specification.

3 Built-in Datatypes and Their Definitions

Built-in Datatype Hierarchy diagram

Diagram showing the derivation relations in the built-in type hierarchy. (A long description of the diagram is available separately.)

anyType all complex types anySimpleType anyAtomicType anyURI base64Binary boolean date dateTime dateTimeStamp decimal integer long int short byte nonNegativeInteger positiveInteger unsignedLong unsignedInt unsignedShort unsignedByte nonPositiveInteger negativeInteger double duration dayTimeDuration yearMonthDuration float gDay gMonth gMonthDay gYear gYearMonth hexBinary NOTATION QName string normalizedString token language Name NCName ENTITY ID IDREF NMTOKEN time ENTITIES IDREFS NMTOKENS
Each built-in datatype defined in this specification can be uniquely addressed via a URI Reference constructed as follows:
  1. the base URI is the URI of the XML Schema namespace
  2. the fragment identifier is the name of the datatype
For example, to address the int datatype, the URI is:
  • http://www.w3.org/2001/XMLSchema#int
Additionally, each facet definition element can be uniquely addressed via a URI constructed as follows:
  1. the base URI is the URI of the XML Schema namespace
  2. the fragment identifier is the name of the facet
For example, to address the maxInclusive facet, the URI is:
  • http://www.w3.org/2001/XMLSchema#maxInclusive
Additionally, each facet usage in a built-in Simple Type Definition can be uniquely addressed via a URI constructed as follows:
  1. the base URI is the URI of the XML Schema namespace
  2. the fragment identifier is the name of the Simple Type Definition, followed by a period ('.') followed by the name of the facet
For example, to address the usage of the maxInclusive facet in the definition of int, the URI is:
  • http://www.w3.org/2001/XMLSchema#int.maxInclusive

next sub-section3.1 Namespace considerations

The ·built-in· datatypes defined by this specification are designed to be used with the XML Schema definition language as well as other XML specifications. To facilitate usage within the XML Schema definition language, the ·built-in· datatypes in this specification have the namespace name:

  • http://www.w3.org/2001/XMLSchema

To facilitate usage in specifications other than the XML Schema definition language, such as those that do not want to know anything about aspects of the XML Schema definition language other than the datatypes, each ·built-in· datatype is also defined in the namespace whose URI is:

  • http://www.w3.org/2001/XMLSchema-datatypes

Each ·user-defined· datatype may also be associated with a target namespace.  If it is constructed from a schema document, then its namespace is typically the target namespace of that schema document. (See XML Representation of Schemas in [XSD 1.1 Part 1: Structures].)

previous sub-section next sub-section3.2 Special Built-in Datatypes

        3.2.1 anySimpleType
            3.2.1.1 Value space
            3.2.1.2 Lexical mapping
            3.2.1.3 Facets
        3.2.2 anyAtomicType
            3.2.2.1 Value space
            3.2.2.2 Lexical mapping
            3.2.2.3 Facets

The two datatypes at the root of the hierarchy of simple types are anySimpleType and anyAtomicType.

3.2.1 anySimpleType

The definition of anySimpleType is a special ·restriction· of anyType.  The ·lexical space· of anySimpleType is the set of all sequences of Unicode characters, and its ·value space· includes all ·atomic values· and all finite-length lists of zero or more ·atomic values·.

For further details of anySimpleType and its representation as a Simple Type Definition, see Built-in Simple Type Definitions (§4.1.6).

3.2.1.1 Value space

The ·value space· of anySimpleType is the set of all ·atomic values· and of all finite-length lists of zero or more ·atomic values·.

Note: It is a consequence of this definition, together with the definition of the ·lexical mapping· in the next section, that some values of this datatype have no ·lexical representation· using the ·lexical mappings· defined by this specification. That is, the "potential" ·value space· and the "effable" or "nameable" ·value space· diverge for this datatype. As far as this specification is concerned, there is no operational difference between the potential and effable ·value spaces· and the distinction is of mostly formal interest. Since some host languages for the type system defined here may allow means of construction values other than mapping from a ·lexical representation·, the difference may have practical importance in some contexts. In those contexts, the term ·value space· should unless otherwise qualified be taken to mean the potential ·value space·.
3.2.1.2 Lexical mapping

The ·lexical space· of anySimpleType is the set of all finite-length sequences of zero or more characters (as defined in [XML]) that ·match· the Char production from [XML]. This is equivalent to the union of the ·lexical spaces· of all ·primitive· and all possible ·ordinary· datatypes.

It is ·implementation-defined· whether an implementation of this specification supports the Char production from [XML], or that from [XML 1.0], or both. See Dependencies on Other Specifications (§1.3).

The ·lexical mapping· of anySimpleType is the union of the ·lexical mappings· of all ·primitive· datatypes and all list datatypes. It will be noted that this mapping is not a function: a given ·literal· may map to one value or to several values of different ·primitive· datatypes, and it may be indeterminate which value is to be preferred in a particular context. When the datatypes defined here are used in the context of [XSD 1.1 Part 1: Structures], the xsi:type attribute defined by that specification in section xsi:type can be used to indicate which value a ·literal· which is the content of an element should map to. In other contexts, other rules (such as type coercion rules) may be employed to determine which value is to be used.

3.2.1.3 Facets

When a new datatype is defined by ·facet-based restriction·, anySimpleType must not be used as the ·base type·. So no ·constraining facets· are directly applicable to anySimpleType.

3.2.2 anyAtomicType

[Definition:]   anyAtomicType is a special ·restriction· of anySimpleType. The ·value· and ·lexical spaces· of anyAtomicType are the unions of the ·value· and ·lexical spaces· of all the ·primitive· datatypes, and anyAtomicType is their ·base type·.

For further details of anyAtomicType and its representation as a Simple Type Definition, see Built-in Simple Type Definitions (§4.1.6).

3.2.2.1 Value space

The ·value space· of anyAtomicType is the union of the ·value spaces· of all the ·primitive· datatypes defined here or supplied as ·implementation-defined· ·primitives·.

3.2.2.2 Lexical mapping

The ·lexical space· of anyAtomicType is the set of all finite-length sequences of zero or more characters (as defined in [XML]) that ·match· the Char production from [XML]. This is equivalent to the union of the ·lexical spaces· of all ·primitive· datatypes.

It is ·implementation-defined· whether an implementation of this specification supports the Char production from [XML], or that from [XML 1.0], or both. See Dependencies on Other Specifications (§1.3).

The ·lexical mapping· of anyAtomicType is the union of the ·lexical mappings· of all ·primitive· datatypes. It will be noted that this mapping is not a function: a given ·literal· may map to one value or to several values of different ·primitive· datatypes, and it may be indeterminate which value is to be preferred in a particular context. When the datatypes defined here are used in the context of [XSD 1.1 Part 1: Structures], the xsi:type attribute defined by that specification in section xsi:type can be used to indicate which value a ·literal· which is the content of an element should map to. In other contexts, other rules (such as type coercion rules) may be employed to determine which value is to be used.

3.2.2.3 Facets

When a new datatype is defined by ·facet-based restriction·, anyAtomicType must not be used as the ·base type·. So no ·constraining facets· are directly applicable to anyAtomicType.

previous sub-section next sub-section3.3 Primitive Datatypes

        3.3.1 string
            3.3.1.1 Value Space
            3.3.1.2 Lexical Mapping
            3.3.1.3 Facets
            3.3.1.4 Derived datatypes
        3.3.2 boolean
            3.3.2.1 Value Space
            3.3.2.2 Lexical Mapping
            3.3.2.3 Facets
        3.3.3 decimal
            3.3.3.1 Lexical Mapping
            3.3.3.2 Facets
            3.3.3.3 Datatypes based on decimal
        3.3.4 float
            3.3.4.1 Value Space
            3.3.4.2 Lexical Mapping
            3.3.4.3 Facets
        3.3.5 double
            3.3.5.1 Value Space
            3.3.5.2 Lexical Mapping
            3.3.5.3 Facets
        3.3.6 duration
            3.3.6.1 Value Space
            3.3.6.2 Lexical Mapping
            3.3.6.3 Facets
            3.3.6.4 Related Datatypes
        3.3.7 dateTime
            3.3.7.1 Value Space
            3.3.7.2 Lexical Mapping
            3.3.7.3 Facets
            3.3.7.4 Related Datatypes
        3.3.8 time
            3.3.8.1 Value Space
            3.3.8.2 Lexical Mappings
            3.3.8.3 Facets
        3.3.9 date
            3.3.9.1 Value Space
            3.3.9.2 Lexical Mapping
            3.3.9.3 Facets
        3.3.10 gYearMonth
            3.3.10.1 Value Space
            3.3.10.2 Lexical Mapping
            3.3.10.3 Facets
        3.3.11 gYear
            3.3.11.1 Value Space
            3.3.11.2 Lexical Mapping
            3.3.11.3 Facets
        3.3.12 gMonthDay
            3.3.12.1 Value Space
            3.3.12.2 Lexical Mapping
            3.3.12.3 Facets
        3.3.13 gDay
            3.3.13.1 Value Space
            3.3.13.2 Lexical Mapping
            3.3.13.3 Facets
        3.3.14 gMonth
            3.3.14.1 Value Space
            3.3.14.2 Lexical Mapping
            3.3.14.3 Facets
        3.3.15 hexBinary
            3.3.15.1 Value Space
            3.3.15.2 Lexical Mapping
            3.3.15.3 Facets
        3.3.16 base64Binary
            3.3.16.1 Value Space
            3.3.16.2 Lexical Mapping
            3.3.16.3 Facets
        3.3.17 anyURI
            3.3.17.1 Value Space
            3.3.17.2 Lexical Mapping
            3.3.17.3 Facets
        3.3.18 QName
            3.3.18.1 Facets
        3.3.19 NOTATION
            3.3.19.1 Facets

The ·primitive· datatypes defined by this specification are described below.  For each datatype, the ·value space· is described; the ·lexical space· is defined using an extended Backus Naur Format grammar (and in most cases also a regular expression using the regular expression language of Regular Expressions (§G)); ·constraining facets· which apply to the datatype are listed; and any datatypes ·constructed· from this datatype are specified.

Conforming processors must support the ·primitive· datatypes defined in this specification; it is ·implementation-defined· whether they support others. ·Primitive· datatypes may be added by revisions to this specification.

Note: Processors may, for example, support the floating-point decimal datatype specified in [Precision Decimal].

3.3.1 string

[Definition:]  The string datatype represents character strings in XML.

Note: Many human languages have writing systems that require child elements for control of aspects such as bidirectional formatting or ruby annotation (see [Ruby] and Section 8.2.4 Overriding the bidirectional algorithm: the BDO element of [HTML 4.01]).  Thus, string, as a simple type that can contain only characters but not child elements, is often not suitable for representing text. In such situations, a complex type that allows mixed content should be considered. For more information, see Section 5.5 Any Element, Any Attribute of [XML Schema Language: Part 0 Primer].
3.3.1.1 Value Space

The ·value space· of string is the set of finite-length sequences of zero or more characters (as defined in [XML]) that ·match· the Char production from [XML]. A character is an atomic unit of communication; it is not further specified except to note that every character has a corresponding Universal Character Set (UCS) code point, which is an integer.

It is ·implementation-defined· whether an implementation of this specification supports the Char production from [XML], or that from [XML 1.0], or both. See Dependencies on Other Specifications (§1.3).

Equality for string is identity. No order is prescribed.

Note: As noted in ordered, the fact that this specification does not specify an order relation for ·string· does not preclude other applications from treating strings as being ordered.
3.3.1.2 Lexical Mapping
The ·lexical space· of string is the set of finite-length sequences of zero or more characters (as defined in [XML]) that ·match· the Char production from [XML].
Lexical Space
[1]   stringRep ::= Char
/* (as defined in [XML]) */

It is ·implementation-defined· whether an implementation of this specification supports the Char production from [XML], or that from [XML 1.0], or both. See Dependencies on Other Specifications (§1.3).

The ·lexical mapping· for string is ·stringLexicalMap·, and the ·canonical mapping· is ·stringCanonicalMap·; each is a subset of the identity function.

3.3.1.3 Facets

The string datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from string may also specify values for the following ·constraining facets·:

The string datatype has the following values for its ·fundamental facets·:

3.3.1.4 Derived datatypes

The following ·built-in· datatype is ·derived· from string

3.3.2 boolean

[Definition:]  boolean represents the values of two-valued logic.

3.3.2.1 Value Space

boolean has the ·value space· of two-valued logic:  {true, false}.

3.3.2.2 Lexical Mapping
boolean's lexical space is a set of four ·literals·:
Lexical Space
[2]   booleanRep ::= 'true' | 'false' | '1' | '0'

The ·lexical mapping· for boolean is ·booleanLexicalMap·; the ·canonical mapping· is ·booleanCanonicalMap·.

3.3.2.3 Facets

The boolean datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from boolean may also specify values for the following ·constraining facets·:

The boolean datatype has the following values for its ·fundamental facets·:

3.3.3 decimal

[Definition:]  decimal represents a subset of the real numbers, which can be represented by decimal numerals. The ·value space· of decimal is the set of numbers that can be obtained by dividing an integer by a non-negative power of ten, i.e., expressible as i / 10n where i and n are integers and n ≥ 0. Precision is not reflected in this value space; the number 2.0 is not distinct from the number 2.00. The order relation on decimal is the order relation on real numbers, restricted to this subset.

Note: For a decimal datatype whose values do reflect precision, see [Precision Decimal].
3.3.3.1 Lexical Mapping

decimal has a lexical representation consisting of a non-empty finite-length sequence of decimal digits (#x30–#x39) separated by a period as a decimal indicator.  An optional leading sign is allowed.  If the sign is omitted, "+" is assumed.  Leading and trailing zeroes are optional.  If the fractional part is zero, the period and following zero(es) can be omitted. For example:  '-1.23', '12678967.543233', '+100000.00', '210'.

The decimal Lexical Representation
[3]   decimalLexicalRep ::= decimalPtNumeral | noDecimalPtNumeral
The lexical space of decimal is the set of lexical representations which match the grammar given above, or (equivalently) the regular expression

(\+|-)?([0-9]+(\.[0-9]*)?|\.[0-9]+)

The mapping from lexical representations to values is the usual one for decimal numerals; it is given formally in ·decimalLexicalMap·.

The definition of the ·canonical representation· has the effect of prohibiting certain options from the Lexical Mapping (§3.3.3.1).  Specifically, for integers, the decimal point and fractional part are prohibited. For other values, the preceding optional "+" sign is prohibited.  The decimal point is required.  In all cases, leading and trailing zeroes are prohibited subject to the following:  there must be at least one digit to the right and to the left of the decimal point which may be a zero.

The mapping from values to ·canonical representations· is given formally in ·decimalCanonicalMap·.

3.3.3.2 Facets

The decimal datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from decimal may also specify values for the following ·constraining facets·:

The decimal datatype has the following values for its ·fundamental facets·:

3.3.3.3 Datatypes based on decimal

The following ·built-in· datatype is ·derived· from decimal

3.3.4 float

[Definition:]  The float datatype is patterned after the IEEE single-precision 32-bit floating point datatype [IEEE 754-2008].  Its value space is a subset of the rational numbers.  Floating point numbers are often used to approximate arbitrary real numbers.

3.3.4.1 Value Space

The ·value space· of float contains the non-zero numbers  m × 2e , where m is an integer whose absolute value is less than 224, and e is an integer between −149 and 104, inclusive.  In addition to these values, the ·value space· of float also contains the following ·special values·positiveZero, negativeZero, positiveInfinity, negativeInfinity, and notANumber.

Note: As explained below, the ·lexical representation· of the float value notANumber is 'NaN'.  Accordingly, in English text we generally use 'NaN' to refer to that value.  Similarly, we use 'INF' and '−INF' to refer to the two values positiveInfinity and negativeInfinity, and '0' and '−0' to refer to positiveZero and negativeZero.
Equality and order for float are defined as follows:
  • Equality is identity, except that  0 = −0  (although they are not identical) and  NaN ≠ NaN  (although NaN is of course identical to itself).
    0 and −0 are thus equivalent for purposes of enumerations and identity constraints, as well as for minimum and maximum values.
  • For the basic values, the order relation on float is the order relation for rational numbers.  INF is greater than all other non-NaN values; −INF is less than all other non-NaN values.  NaN is ·incomparable· with any value in the ·value space· including itself.  0 and −0 are greater than all the negative numbers and less than all the positive numbers.
Note: Any value ·incomparable· with the value used for the four bounding facets (·minInclusive·, ·maxInclusive·, ·minExclusive·, and ·maxExclusive·) will be excluded from the resulting restricted ·value space·.  In particular, when NaN is used as a facet value for a bounding facet, since no float values are ·comparable· with it, the result is a ·value space· that is empty.  If any other value is used for a bounding facet, NaN will be excluded from the resulting restricted ·value space·; to add NaN back in requires union with the NaN-only space (which may be derived using the pattern 'NaN').
Note: The Schema 1.0 version of this datatype did not differentiate between 0 and −0 and NaN was equal to itself.  The changes were made to make the datatype more closely mirror [IEEE 754-2008].
3.3.4.2 Lexical Mapping
The ·lexical space· of float is the set of all decimal numerals with or without a decimal point, numerals in scientific (exponential) notation, and the ·literals· 'INF', '+INF', '-INF', and 'NaN' The floatRep production is equivalent to this regular expression (after whitespace is removed from the regular expression):

(\+|-)?([0-9]+(\.[0-9]*)?|\.[0-9]+)([Ee](\+|-)?[0-9]+)?
|(\+|-)?INF|NaN

The float datatype is designed to implement for schema processing the single-precision floating-point datatype of [IEEE 754-2008].  That specification does not specify specific ·lexical representations·, but does prescribe requirements on any ·lexical mapping· used.  Any ·lexical mapping· that maps the ·lexical space· just described onto the ·value space·, is a function, satisfies the requirements of [IEEE 754-2008], and correctly handles the mapping of the literals 'INF', 'NaN', etc., to the ·special values·, satisfies the conformance requirements of this specification.

Since IEEE allows some variation in rounding of values, processors conforming to this specification may exhibit some variation in their ·lexical mappings·.

The ·lexical mapping· ·floatLexicalMap· is provided as an example of a simple algorithm that yields a conformant mapping, and that provides the most accurate rounding possible—and is thus useful for insuring inter-implementation reproducibility and inter-implementation round-tripping.  The simple rounding algorithm used in ·floatLexicalMap· may be more efficiently implemented using the algorithms of [Clinger, WD (1990)].

Note: The Schema 1.0 version of this datatype did not permit rounding algorithms whose results differed from [Clinger, WD (1990)].

The ·canonical mapping· ·floatCanonicalMap· is provided as an example of a mapping that does not produce unnecessarily long ·canonical representations·.  Other algorithms which do not yield identical results for mapping from float values to character strings are permitted by [IEEE 754-2008].

3.3.4.3 Facets

The float datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from float may also specify values for the following ·constraining facets·:

The float datatype has the following values for its ·fundamental facets·:

3.3.5 double

[Definition:]  The double datatype is patterned after the IEEE double-precision 64-bit floating point datatype [IEEE 754-2008].  Each floating point datatype has a value space that is a subset of the rational numbers.  Floating point numbers are often used to approximate arbitrary real numbers.

Note: The only significant differences between float and double are the three defining constants 53 (vs 24), −1074 (vs −149), and 971 (vs 104).
3.3.5.1 Value Space

The ·value space· of double contains the non-zero numbers  m × 2e , where m is an integer whose absolute value is less than 253, and e is an integer between −1074 and 971, inclusive.  In addition to these values, the ·value space· of double also contains the following ·special values·positiveZero, negativeZero, positiveInfinity, negativeInfinity, and notANumber.

Note: As explained below, the ·lexical representation· of the double value notANumber is 'NaN'.  Accordingly, in English text we generally use 'NaN' to refer to that value.  Similarly, we use 'INF' and '−INF' to refer to the two values positiveInfinity and negativeInfinity, and '0' and '−0' to refer to positiveZero and negativeZero.
Equality and order for double are defined as follows:
  • Equality is identity, except that  0 = −0  (although they are not identical) and  NaN ≠ NaN  (although NaN is of course identical to itself).
    0 and −0 are thus equivalent for purposes of enumerations, identity constraints, and minimum and maximum values.
  • For the basic values, the order relation on double is the order relation for rational numbers.  INF is greater than all other non-NaN values; −INF is less than all other non-NaN values.  NaN is ·incomparable· with any value in the ·value space· including itself.  0 and −0 are greater than all the negative numbers and less than all the positive numbers.
Note: Any value ·incomparable· with the value used for the four bounding facets (·minInclusive·, ·maxInclusive·, ·minExclusive·, and ·maxExclusive·) will be excluded from the resulting restricted ·value space·.  In particular, when NaN is used as a facet value for a bounding facet, since no double values are ·comparable· with it, the result is a ·value space· that is empty.  If any other value is used for a bounding facet, NaN will be excluded from the resulting restricted ·value space·; to add NaN back in requires union with the NaN-only space (which may be derived using the pattern 'NaN').
Note: The Schema 1.0 version of this datatype did not differentiate between 0 and −0 and NaN was equal to itself.  The changes were made to make the datatype more closely mirror [IEEE 754-2008].
3.3.5.2 Lexical Mapping
The ·lexical space· of double is the set of all decimal numerals with or without a decimal point, numerals in scientific (exponential) notation, and the ·literals· 'INF', '+INF', '-INF', and 'NaN' The doubleRep production is equivalent to this regular expression (after whitespace is eliminated from the expression):

(\+|-)?([0-9]+(\.[0-9]*)?|\.[0-9]+)([Ee](\+|-)?[0-9]+)? |(\+|-)?INF|NaN

The double datatype is designed to implement for schema processing the double-precision floating-point datatype of [IEEE 754-2008].  That specification does not specify specific ·lexical representations·, but does prescribe requirements on any ·lexical mapping· used.  Any ·lexical mapping· that maps the ·lexical space· just described onto the ·value space·, is a function, satisfies the requirements of [IEEE 754-2008], and correctly handles the mapping of the literals 'INF', 'NaN', etc., to the ·special values·, satisfies the conformance requirements of this specification.

Since IEEE allows some variation in rounding of values, processors conforming to this specification may exhibit some variation in their ·lexical mappings·.

The ·lexical mapping· ·doubleLexicalMap· is provided as an example of a simple algorithm that yields a conformant mapping, and that provides the most accurate rounding possible—and is thus useful for insuring inter-implementation reproducibility and inter-implementation round-tripping.  The simple rounding algorithm used in ·doubleLexicalMap· may be more efficiently implemented using the algorithms of [Clinger, WD (1990)].

Note: The Schema 1.0 version of this datatype did not permit rounding algorithms whose results differed from [Clinger, WD (1990)].

The ·canonical mapping· ·doubleCanonicalMap· is provided as an example of a mapping that does not produce unnecessarily long ·canonical representations·.  Other algorithms which do not yield identical results for mapping from float values to character strings are permitted by [IEEE 754-2008].

3.3.5.3 Facets

The double datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from double may also specify values for the following ·constraining facets·:

The double datatype has the following values for its ·fundamental facets·:

3.3.6 duration

[Definition:]  duration is a datatype that represents durations of time.  The concept of duration being captured is drawn from those of [ISO 8601], specifically durations without fixed endpoints.  For example, "15 days" (whose most common lexical representation in duration is "'P15D'") is a duration value; "15 days beginning 12 July 1995" and "15 days ending 12 July 1995" are not duration values.  duration can provide addition and subtraction operations between duration values and between duration/dateTime value pairs, and can be the result of subtracting dateTime values.  However, only addition to dateTime is required for XML Schema processing and is defined in the function ·dateTimePlusDuration·.

3.3.6.1 Value Space
Duration values can be modelled as two-property tuples. Each value consists of an integer number of months and a decimal number of seconds. The ·seconds· value must not be negative if the ·months· value is positive and must not be positive if the ·months· is negative.
Properties of duration Values
a decimal value; must not be negative if ·months· is positive, and must not be positive if ·months· is negative.
duration is partially ordered.  Equality of duration is defined in terms of equality of dateTime; order for duration is defined in terms of the order of dateTime. Specifically, the equality or order of two duration values is determined by adding each duration in the pair to each of the following four dateTime values:
  • 1696-09-01T00:00:00Z
  • 1697-02-01T00:00:00Z
  • 1903-03-01T00:00:00Z
  • 1903-07-01T00:00:00Z
If all four resulting dateTime value pairs are ordered the same way (less than, equal, or greater than), then the original pair of duration values is ordered the same way; otherwise the original pair is ·incomparable·.
Note: These four values are chosen so as to maximize the possible differences in results that could occur, such as the difference when adding P1M and P30D:  1697-02-01T00:00:00Z + P1M < 1697-02-01T00:00:00Z + P30D , but 1903-03-01T00:00:00Z + P1M > 1903-03-01T00:00:00Z + P30D , so that  P1M <> P30D .  If two duration values are ordered the same way when added to each of these four dateTime values, they will retain the same order when added to any other dateTime values.  Therefore, two duration values are incomparable if and only if they can ever result in different orders when added to any dateTime value.

Under the definition just given, two duration values are equal if and only if they are identical.

Note: Two totally ordered datatypes (yearMonthDuration and dayTimeDuration) are derived from duration in Other Built-in Datatypes (§3.4).
Note: There are many ways to implement duration, some of which do not base the implementation on the two-component model.  This specification does not prescribe any particular implementation, as long as the visible results are isomorphic to those described herein.
Note: See the conformance notes in Partial Implementation of Infinite Datatypes (§5.4), which apply to this datatype.
3.3.6.2 Lexical Mapping
The ·lexical representations· of duration are more or less based on the pattern:

PnYnMnDTnHnMnS

More precisely, the ·lexical space· of duration is the set of character strings that satisfy durationLexicalRep as defined by the following productions:
Lexical Representation Fragments
[6]   duYearFrag ::= unsignedNoDecimalPtNumeral 'Y'
[7]   duMonthFrag ::= unsignedNoDecimalPtNumeral 'M'
[8]   duDayFrag ::= unsignedNoDecimalPtNumeral 'D'
[9]   duHourFrag ::= unsignedNoDecimalPtNumeral 'H'
[10]   duMinuteFrag ::= unsignedNoDecimalPtNumeral 'M'
[11]   duSecondFrag ::= (unsignedNoDecimalPtNumeral | unsignedDecimalPtNumeral) 'S'
[12]   duYearMonthFrag ::= (duYearFrag duMonthFrag?) | duMonthFrag
[13]   duTimeFrag ::= 'T' ((duHourFrag duMinuteFragduSecondFrag?) | (duMinuteFrag duSecondFrag?) | duSecondFrag)
[14]   duDayTimeFrag ::= (duDayFrag duTimeFrag?) | duTimeFrag
Lexical Representation
[15]   durationLexicalRep ::= '-'? 'P' ((duYearMonthFrag duDayTimeFrag?) | duDayTimeFrag)

Thus, a durationLexicalRep consists of one or more of a duYearFrag, duMonthFrag, duDayFrag, duHourFrag, duMinuteFrag, and/or duSecondFrag, in order, with letters 'P' and 'T' (and perhaps a '-') where appropriate.

The language accepted by the durationLexicalRep production is the set of strings which satisfy all of the following three regular expressions:
  • The expression

    -?P[0-9]+Y?([0-9]+M)?([0-9]+D)?(T([0-9]+H)?([0-9]+M)?([0-9]+(\.[0-9]+)?S)?)?

    matches only strings in which the fields occur in the proper order.
  • The expression '.*[YMDHS].*' matches only strings in which at least one field occurs.
  • The expression '.*[^T]' matches only strings in which 'T' is not the final character, so that if 'T' appears, something follows it. The first rule ensures that what follows 'T' will be an hour, minute, or second field.
The intersection of these three regular expressions is equivalent to the following (after removal of the white space inserted here for legibility):
-?P( ( ( [0-9]+Y([0-9]+M)?([0-9]+D)?
       | ([0-9]+M)([0-9]+D)?
       | ([0-9]+D)
       )
       (T ( ([0-9]+H)([0-9]+M)?([0-9]+(\.[0-9]+)?S)?
          | ([0-9]+M)([0-9]+(\.[0-9]+)?S)?
          | ([0-9]+(\.[0-9]+)?S)
          )
       )?
    )
  | (T ( ([0-9]+H)([0-9]+M)?([0-9]+(\.[0-9]+)?S)?
       | ([0-9]+M)([0-9]+(\.[0-9]+)?S)?
       | ([0-9]+(\.[0-9]+)?S)
       )
    )
  )

The ·lexical mapping· for duration is ·durationMap·.

·The canonical mapping· for duration is ·durationCanonicalMap·.

3.3.6.3 Facets

The duration datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from duration may also specify values for the following ·constraining facets·:

The duration datatype has the following values for its ·fundamental facets·:

3.3.6.4 Related Datatypes

The following ·built-in· datatypes are ·derived· from duration

3.3.7 dateTime

dateTime represents instants of time, optionally marked with a particular time zone offset.  Values representing the same instant but having different time zone offsets are equal but not identical.

3.3.7.1 Value Space

dateTime uses the date/timeSevenPropertyModel, with no properties except ·timezoneOffset· permitted to be absent. The ·timezoneOffset· property remains ·optional·.

Note: In version 1.0 of this specification, the ·year· property was not permitted to have the value zero. The year before the year 1 in the proleptic Gregorian calendar, traditionally referred to as 1 BC or as 1 BCE, was represented by a ·year· value of −1, 2 BCE by −2, and so forth. Of course, many, perhaps most, references to 1 BCE (or 1 BC) actually refer not to a year in the proleptic Gregorian calendar but to a year in the Julian or "old style" calendar; the two correspond approximately but not exactly to each other.
In this version of this specification, two changes are made in order to agree with existing usage. First, ·year· is permitted to have the value zero. Second, the interpretation of ·year· values is changed accordingly: a ·year· value of zero represents 1 BCE, −1 represents 2 BCE, etc. This representation simplifies interval arithmetic and leap-year calculation for dates before the common era (which may be why astronomers and others interested in such calculations with the proleptic Gregorian calendar have adopted it), and is consistent with the current edition of [ISO 8601].
Note that 1 BCE, 5 BCE, and so on (years 0000, -0004, etc. in the lexical representation defined here) are leap years in the proleptic Gregorian calendar used for the date/time datatypes defined here. Version 1.0 of this specification was unclear about the treatment of leap years before the common era. If existing schemas or data specify dates of 29 February for any years before the common era, then some values giving a date of 29 February which were valid under a plausible interpretation of XSD 1.0 will be invalid under this specification, and some which were invalid will be valid. With that possible exception, schemas and data valid under the old interpretation remain valid under the new.
Constraint: Day-of-month Values
The ·day· value must be no more than 30 if ·month· is one of 4, 6, 9, or 11; no more than 28 if ·month· is 2 and ·year· is not divisible by 4, or is divisible by 100 but not by 400; and no more than 29 if ·month· is 2 and ·year· is divisible by 400, or by 4 but not by 100.
Note: See the conformance note in Partial Implementation of Infinite Datatypes (§5.4) which applies to the ·year· and ·second· values of this datatype.

Equality and order are as prescribed in The Seven-property Model (§D.2.1)dateTime values are ordered by their ·timeOnTimeline· value.

Note: Since the order of a dateTime value having a ·timezoneOffset· relative to another value whose ·timezoneOffset· is absent is determined by imputing time zone offsets of both +14:00 and −14:00 to the value with no time zone offset, many such combinations will be ·incomparable· because the two imputed time zone offsets yield different orders.
Although dateTime and other types related to dates and times have only a partial order, it is possible for datatypes derived from dateTime to have total orders, if they are restricted (e.g. using the pattern facet) to the subset of values with, or the subset of values without, time zone offsets. Similar restrictions on other date- and time-related types will similarly produce totally ordered subtypes. Note, however, that such restrictions do not affect the value shown, for a given Simple Type Definition, in the ordered facet.
Note: Order and equality are essentially the same for dateTime in this version of this specification as they were in version 1.0.  However, since values now distinguish time zone offsets, equal values with different ·timezoneOffset·s are not identical, and values with extreme ·timezoneOffset·s may no longer be equal to any value with a smaller ·timezoneOffset·.
3.3.7.2 Lexical Mapping
The lexical representations for dateTime are as follows:
Lexical Space
[16]   dateTimeLexicalRep ::= yearFrag '-monthFrag '-dayFrag 'T' ((hourFrag ':minuteFrag ':secondFrag) | endOfDayFrag) timezoneFrag?   Constraint:  Day-of-month Representations
Constraint: Day-of-month Representations
Within a dateTimeLexicalRep, a dayFrag must not begin with the digit '3' or be '29' unless the value to which it would map would satisfy the value constraint on ·day· values ("Constraint: Day-of-month Values") given above.
In such representations:
  • yearFrag is a numeral consisting of at least four decimal digits, optionally preceded by a minus sign; leading '0' digits are prohibited except to bring the digit count up to four.  It represents the ·year· value.
  • Subsequent '-', 'T', and ':', separate the various numerals.
  • monthFrag, dayFrag, hourFrag, and minuteFrag are numerals consisting of exactly two decimal digits.  They represent the ·month·, ·day·, ·hour·, and ·minute· values respectively.
  • secondFrag is a numeral consisting of exactly two decimal digits, or two decimal digits, a decimal point, and one or more trailing digits.  It represents the ·second· value.
  • Alternatively, endOfDayFrag combines the hourFrag, minuteFrag, minuteFrag, and their separators to represent midnight of the day, which is the first moment of the next day.
  • timezoneFrag, if present, specifies an offset between UTC and local time. Time zone offsets are a count of minutes (expressed in timezoneFrag as a count of hours and minutes) that are added or subtracted from UTC time to get the "local" time.  'Z' is an alternative representation of the time zone offset '00:00', which is, of course, zero minutes from UTC.
    For example, 2002-10-10T12:00:00−05:00 (noon on 10 October 2002, Central Daylight Savings Time as well as Eastern Standard Time in the U.S.) is equal to 2002-10-10T17:00:00Z, five hours later than 2002-10-10T12:00:00Z.
    Note: For the most part, this specification adopts the distinction between 'timezone' and 'timezone offset' laid out in [Timezones]. Version 1.0 of this specification did not make this distinction, but used the term 'timezone' for the time zone offset information associated with date- and time-related datatypes. Some traces of the earlier usage remain visible in this and other specifications. The names timezoneFrag and explicitTimezone are such traces ; others will be found in the names of functions defined in [XQuery 1.0 and XPath 2.0 Functions and Operators], or in references in this specification to "timezoned" and "non-timezoned" values.
The dateTimeLexicalRep production is equivalent to this regular expression once whitespace is removed.
-?([1-9][0-9]{3,}|0[0-9]{3})
-(0[1-9]|1[0-2])
-(0[1-9]|[12][0-9]|3[01])
T(([01][0-9]|2[0-3]):[0-5][0-9]:[0-5][0-9](\.[0-9]+)?|(24:00:00(\.0+)?))
(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?
Note that neither the dateTimeLexicalRep production nor this regular expression alone enforce the constraint on dateTimeLexicalRep given above.

The ·lexical mapping· for dateTime is ·dateTimeLexicalMap·. The ·canonical mapping· is ·dateTimeCanonicalMap·.

3.3.7.3 Facets

The dateTime datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The dateTime datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from dateTime may also specify values for the following ·constraining facets·:

The dateTime datatype has the following values for its ·fundamental facets·:

3.3.7.4 Related Datatypes

The following ·built-in· datatype is ·derived· from dateTime

3.3.8 time

time represents instants of time that recur at the same point in each calendar day, or that occur in some arbitrary calendar day.

3.3.8.1 Value Space

time uses the date/timeSevenPropertyModel, with ·year·, ·month·, and ·day· required to be absent·timezoneOffset· remains ·optional·.

Note: See the conformance note in Partial Implementation of Infinite Datatypes (§5.4) which applies to the ·second· value of this datatype.

Equality and order are as prescribed in The Seven-property Model (§D.2.1)time values (points in time in an "arbitrary" day) are ordered taking into account their ·timezoneOffset·.

A calendar (or "local time") day with a larger positive time zone offset begins earlier than the same calendar day with a smaller (or negative) time zone offset. Since the time zone offsets allowed spread over 28 hours, it is possible for the period denoted by a given calendar day with one time zone offset to be completely disjoint from the period denoted by the same calendar day with a different offset — the earlier day ends before the later one starts.  The moments in time represented by a single calendar day are spread over a 52-hour interval, from the beginning of the day in the +14:00 time zone offset to the end of that day in the −14:00 time zone offset.

Note: The relative order of two time values, one of which has a ·timezoneOffset· of absent is determined by imputing time zone offsets of both +14:00 and −14:00 to the value without an offset. Many such combinations will be ·incomparable· because the two imputed time zone offsets yield different orders.  However, for a given non-timezoned value, there will always be timezoned values at one or both ends of the 52-hour interval that are ·comparable· (because the interval of ·incomparability· is only 28 hours wide).
Some pairs of time literals which in the 1.0 version of this specification denoted the same value now (in this version) denote distinct values instead, because values now include time zone offset information. Some such pairs, such as '05:00:00-03:00' and '10:00:00+02:00', now denote equal though distinct values (because they identify the same points on the time line); others, such as '23:00:00-03:00' and '02:00:00Z', now denote unequal values (23:00:00−03:00 > 02:00:00Z because 23:00:00−03:00 on any given day is equal to 02:00:00Z on the next day).
3.3.8.2 Lexical Mappings
The lexical representations for time are "projections" of those of dateTime, as follows:
Lexical Space
[17]   timeLexicalRep ::= ((hourFrag ':minuteFrag ':secondFrag) | endOfDayFrag) timezoneFrag?
The timeLexicalRep production is equivalent to this regular expression, once whitespace is removed:

(([01][0-9]|2[0-3]):[0-5][0-9]:[0-5][0-9](\.[0-9]+)?|(24:00:00(\.0+)?))(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?

Note that neither the timeLexicalRep production nor this regular expression alone enforce the constraint on timeLexicalRep given above.

The ·lexical mapping· for time is ·timeLexicalMap·; the ·canonical mapping· is ·timeCanonicalMap·.

Note: The ·lexical mapping· maps '00:00:00' and '24:00:00' to the same value, namely midnight (·hour· = 0 , ·minute· = 0 , ·second· = 0).
3.3.8.3 Facets

The time datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The time datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from time may also specify values for the following ·constraining facets·:

The time datatype has the following values for its ·fundamental facets·:

3.3.9 date

[Definition:]   date represents top-open intervals of exactly one day in length on the timelines of dateTime, beginning on the beginning moment of each day, up to but not including the beginning moment of the next day).  For non-timezoned values, the top-open intervals disjointly cover the non-timezoned timeline, one per day.  For timezoned values, the intervals begin at every minute and therefore overlap.

3.3.9.1 Value Space

date uses the date/timeSevenPropertyModel, with ·hour·, ·minute·, and ·second· required to be absent·timezoneOffset· remains ·optional·.

Constraint: Day-of-month Values
The ·day· value must be no more than 30 if ·month· is one of 4, 6, 9, or 11, no more than 28 if ·month· is 2 and ·year· is not divisible by 4, or is divisible by 100 but not by 400, and no more than 29 if ·month· is 2 and ·year· is divisible by 400, or by 4 but not by 100.
Note: See the conformance note in Partial Implementation of Infinite Datatypes (§5.4) which applies to the ·year· value of this datatype.

Equality and order are as prescribed in The Seven-property Model (§D.2.1).

Note: In version 1.0 of this specification, date values did not retain a time zone offset explicitly, but for offsets not too far from zero their time zone offset could be recovered based on their value's first moment on the timeline.  The date/timeSevenPropertyModel retains all time zone offsets.
Some date values with different time zone offsets that were identical in the 1.0 version of this specification, such as 2000-01-01+13:00 and 1999-12-31−11:00, are in this version of this specification equal (because they begin at the same moment on the time line) but are not identical (because they have and retain different time zone offsets).  This situation will arise for dates only if one has a far-from-zero time zone offset and hence in 1.0 its "recoverable time zone offset" was different from the the time zone offset which is retained in the date/timeSevenPropertyModel used in this version of this specification.
3.3.9.2 Lexical Mapping
The lexical representations for date are "projections" of those of dateTime, as follows:
Lexical Space
[18]   dateLexicalRep ::= yearFrag '-monthFrag '-dayFrag timezoneFrag?   Constraint:  Day-of-month Representations
Constraint: Day-of-month Representations
Within a dateLexicalRep, a dayFrag must not begin with the digit '3' or be '29' unless the value to which it would map would satisfy the value constraint on ·day· values ("Constraint: Day-of-month Values") given above.
The dateLexicalRep production is equivalent to this regular expression:

-?([1-9][0-9]{3,}|0[0-9]{3})-(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?

Note that neither the dateLexicalRep production nor this regular expression alone enforce the constraint on dateLexicalRep given above.

The ·lexical mapping· for date is ·dateLexicalMap·. The ·canonical mapping· is ·dateCanonicalMap·.

3.3.9.3 Facets

The date datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The date datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from date may also specify values for the following ·constraining facets·:

The date datatype has the following values for its ·fundamental facets·:

3.3.10 gYearMonth

gYearMonth represents specific whole Gregorian months in specific Gregorian years.

Note: Because month/year combinations in one calendar only rarely correspond to month/year combinations in other calendars, values of this type are not, in general, convertible to simple values corresponding to month/year combinations in other calendars.  This type should therefore be used with caution in contexts where conversion to other calendars is desired.
3.3.10.1 Value Space

gYearMonth uses the date/timeSevenPropertyModel, with ·day·, ·hour·, ·minute·, and ·second· required to be absent·timezoneOffset· remains ·optional·.

Note: See the conformance note in Partial Implementation of Infinite Datatypes (§5.4) which applies to the ·year· value of this datatype.

Equality and order are as prescribed in The Seven-property Model (§D.2.1).

3.3.10.2 Lexical Mapping
The lexical representations for gYearMonth are "projections" of those of dateTime, as follows:
Lexical Space
[19]   gYearMonthLexicalRep ::= yearFrag '-monthFrag timezoneFrag?
The gYearMonthLexicalRep is equivalent to this regular expression:

-?([1-9][0-9]{3,}|0[0-9]{3})-(0[1-9]|1[0-2])(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?

The ·lexical mapping· for gYearMonth is ·gYearMonthLexicalMap·. The ·canonical mapping· is ·gYearMonthCanonicalMap·.

3.3.10.3 Facets

The gYearMonth datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The gYearMonth datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from gYearMonth may also specify values for the following ·constraining facets·:

The gYearMonth datatype has the following values for its ·fundamental facets·:

3.3.11 gYear

gYear represents Gregorian calendar years.

Note: Because years in one calendar only rarely correspond to years in other calendars, values of this type are not, in general, convertible to simple values corresponding to years in other calendars.  This type should therefore be used with caution in contexts where conversion to other calendars is desired.
3.3.11.1 Value Space

gYear uses the date/timeSevenPropertyModel, with ·month·, ·day·, ·hour·, ·minute·, and ·second· required to be absent·timezoneOffset· remains ·optional·.

Note: See the conformance note in Partial Implementation of Infinite Datatypes (§5.4) which applies to the ·year· value of this datatype.

Equality and order are as prescribed in The Seven-property Model (§D.2.1).

3.3.11.2 Lexical Mapping
The lexical representations for gYear are "projections" of those of dateTime, as follows:
Lexical Space
[20]   gYearLexicalRep ::= yearFrag timezoneFrag?
The gYearLexicalRep is equivalent to this regular expression:

-?([1-9][0-9]{3,}|0[0-9]{3})(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?

The ·lexical mapping· for gYear is ·gYearLexicalMap·. The ·canonical mapping· is ·gYearCanonicalMap·.

3.3.11.3 Facets

The gYear datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The gYear datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from gYear may also specify values for the following ·constraining facets·:

The gYear datatype has the following values for its ·fundamental facets·:

3.3.12 gMonthDay

gMonthDay represents whole calendar days that recur at the same point in each calendar year, or that occur in some arbitrary calendar year.  (Obviously, days beyond 28 cannot occur in all Februaries; 29 is nonetheless permitted.)

This datatype can be used, for example, to record birthdays; an instance of the datatype could be used to say that someone's birthday occurs on the 14th of September every year.

Note: Because day/month combinations in one calendar only rarely correspond to day/month combinations in other calendars, values of this type do not, in general, have any straightforward or intuitive representation in terms of most other calendars. This type should therefore be used with caution in contexts where conversion to other calendars is desired.
3.3.12.1 Value Space

gMonthDay uses the date/timeSevenPropertyModel, with ·year·, ·hour·, ·minute·, and ·second· required to be absent·timezoneOffset· remains ·optional·.

Constraint: Day-of-month Values
The ·day· value must be no more than 30 if ·month· is one of 4, 6, 9, or 11, and no more than 29 if ·month· is 2.

Equality and order are as prescribed in The Seven-property Model (§D.2.1).

Note: In version 1.0 of this specification, gMonthDay values did not retain a time zone offset explicitly, but for time zone offsets not too far from ·UTC· their time zone offset could be recovered based on their value's first moment on the timeline.  The date/timeSevenPropertyModel retains all time zone offsets.
An example that shows the difference from version 1.0 (see Lexical Mapping (§3.3.12.2) for the notations):
  • A day is a calendar (or "local time") day offset from ·UTC· by the appropriate interval; this is now true for all ·day· values, including those with time zone offsets outside the range +12:00 through -11:59 inclusive:
    --12-12+13:00 < --12-12+11:00  (just as --12-12+12:00 has always been less than --12-12+11:00, but in version 1.0  --12-12+13:00 > --12-12+11:00 , since --12-12+13:00's "recoverable time zone offset" was −11:00)
3.3.12.2 Lexical Mapping
The lexical representations for gMonthDay are "projections" of those of dateTime, as follows:
Lexical Space
[21]   gMonthDayLexicalRep ::= '--monthFrag '-dayFrag timezoneFrag?   Constraint:  Day-of-month Representations
Constraint: Day-of-month Representations
Within a gMonthDayLexicalRep, a dayFrag must not begin with the digit '3' or be '29' unless the value to which it would map would satisfy the value constraint on ·day· values ("Constraint: Day-of-month Values") given above.
The gMonthDayLexicalRep is equivalent to this regular expression:

--(0[1-9]|1[0-2])-(0[1-9]|[12][0-9]|3[01])(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?

Note that neither the gMonthDayLexicalRep production nor this regular expression alone enforce the constraint on gMonthDayLexicalRep given above.

The ·lexical mapping· for gMonthDay is ·gMonthDayLexicalMap·. The ·canonical mapping· is ·gMonthDayCanonicalMap·.

3.3.12.3 Facets

The gMonthDay datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The gMonthDay datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from gMonthDay may also specify values for the following ·constraining facets·:

The gMonthDay datatype has the following values for its ·fundamental facets·:

3.3.13 gDay

[Definition:]  gDay represents whole days within an arbitrary month—days that recur at the same point in each (Gregorian) month. This datatype is used to represent a specific day of the month. To indicate, for example, that an employee gets a paycheck on the 15th of each month.  (Obviously, days beyond 28 cannot occur in all months; they are nonetheless permitted, up to 31.)

Note: Because days in one calendar only rarely correspond to days in other calendars, gDay values do not, in general, have any straightforward or intuitive representation in terms of most non-Gregorian calendars. gDay should therefore be used with caution in contexts where conversion to other calendars is desired.
3.3.13.1 Value Space

gDay uses the date/timeSevenPropertyModel, with ·year·, ·month·, ·hour·, ·minute·, and ·second· required to be absent·timezoneOffset· remains ·optional· and ·day· must be between 1 and 31 inclusive.

Equality and order are as prescribed in The Seven-property Model (§D.2.1).  Since gDay values (days) are ordered by their first moments, it is possible for apparent anomalies to appear in the order when ·timezoneOffset· values differ by at least 24 hours.  (It is possible for ·timezoneOffset· values to differ by up to 28 hours.)

Examples that may appear anomalous (see Lexical Mapping (§3.3.13.2) for the notations):
  • ---15 < ---16 , but  ---15−13:00 > ---16+13:00
  • ---15−11:00 = ---16+13:00
  • ---15−13:00 <> ---16 , because  ---15−13:00 > ---16+14:00  and ---15−13:00 < 16−14:00
Note: Time zone offsets do not cause wrap-around at the end of the month:  the last day of a given month with a time zone offset of −13:00 may start after the first day of the next month with offset +13:00, as measured on the global timeline, but nonetheless  ---01+13:00 < ---31−13:00 .
3.3.13.2 Lexical Mapping
The lexical representations for gDay are "projections" of those of dateTime, as follows:
Lexical Space
[22]   gDayLexicalRep ::= '---dayFrag timezoneFrag?
The gDayLexicalRep is equivalent to this regular expression:

---(0[1-9]|[12][0-9]|3[01])(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?

The ·lexical mapping· for gDay is ·gDayLexicalMap·. The ·canonical mapping· is ·gDayCanonicalMap·.

3.3.13.3 Facets

The gDay datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The gDay datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from gDay may also specify values for the following ·constraining facets·:

The gDay datatype has the following values for its ·fundamental facets·:

3.3.14 gMonth

gMonth represents whole (Gregorian) months within an arbitrary year—months that recur at the same point in each year.  It might be used, for example, to say what month annual Thanksgiving celebrations fall in different countries (--11 in the United States, --10 in Canada, and possibly other months in other countries).

Note: Because months in one calendar only rarely correspond to months in other calendars, values of this type do not, in general, have any straightforward or intuitive representation in terms of most other calendars. This type should therefore be used with caution in contexts where conversion to other calendars is desired.
3.3.14.1 Value Space

gMonth uses the date/timeSevenPropertyModel, with ·year·, ·day·, ·hour·, ·minute·, and ·second· required to be absent·timezoneOffset· remains ·optional·.

Equality and order are as prescribed in The Seven-property Model (§D.2.1).

3.3.14.2 Lexical Mapping
The lexical representations for gMonth are "projections" of those of dateTime, as follows:
Lexical Space
[23]   gMonthLexicalRep ::= '--monthFrag timezoneFrag?
The gMonthLexicalRep is equivalent to this regular expression:

--(0[1-9]|1[0-2])(Z|(\+|-)((0[0-9]|1[0-3]):[0-5][0-9]|14:00))?

The ·lexical mapping· for gMonth is ·gMonthLexicalMap·. The ·canonical mapping· is ·gMonthCanonicalMap·.

3.3.14.3 Facets

The gMonth datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The gMonth datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from gMonth may also specify values for the following ·constraining facets·:

The gMonth datatype has the following values for its ·fundamental facets·:

3.3.15 hexBinary

[Definition:]  hexBinary represents arbitrary hex-encoded binary data. 

3.3.15.1 Value Space

The ·value space· of hexBinary is the set of finite-length sequences of zero or more binary octets.  The length of a value is the number of octets.

3.3.15.2 Lexical Mapping

hexBinary's ·lexical space· consists of strings of hex (hexadecimal) digits, two consecutive digits representing each octet in the corresponding value (treating the octet as the binary representation of a number between 0 and 255).  For example, '0FB7' is a ·lexical representation· of the two-octet value 00001111 10110111.

More formally, the ·lexical space· of hexBinary is the set of literals matching the hexBinary production.
Lexical space of hexBinary
[24]   hexDigit ::= [0-9a-fA-F]
[25]   hexOctet ::= hexDigit hexDigit
[26]   hexBinary ::= hexOctet*

The set recognized by hexBinary is the same as that recognized by the regular expression '([0-9a-fA-F]{2})*'.

The ·lexical mapping· of hexBinary is ·hexBinaryMap·.

The ·canonical mapping· of hexBinary is given formally in ·hexBinaryCanonical·.

3.3.15.3 Facets

The hexBinary datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from hexBinary may also specify values for the following ·constraining facets·:

The hexBinary datatype has the following values for its ·fundamental facets·:

3.3.16 base64Binary

[Definition:]   base64Binary represents arbitrary Base64-encoded binary data.  For base64Binary data the entire binary stream is encoded using the Base64 Encoding defined in [RFC 3548], which is derived from the encoding described in [RFC 2045].

3.3.16.1 Value Space

The ·value space· of base64Binary is the set of finite-length sequences of zero or more binary octets.  The length of a value is the number of octets.

3.3.16.2 Lexical Mapping

The ·lexical representations· of base64Binary values are limited to the 65 characters of the Base64 Alphabet defined in [RFC 3548], i.e., a-z, A-Z, 0-9, the plus sign (+), the forward slash (/) and the equal sign (=), together with the space character (#x20). No other characters are allowed.

For compatibility with older mail gateways, [RFC 2045] suggests that Base64 data should have lines limited to at most 76 characters in length.  This line-length limitation is not required by [RFC 3548] and is not mandated in the ·lexical representations· of base64Binary data.  It must not be enforced by XML Schema processors.

The ·lexical space· of base64Binary is the set of literals which ·match· the base64Binaryproduction.

Lexical space of base64Binary
[27]   Base64Binary ::= (B64quad* B64final)?
[28]   B64quad ::= (B64 B64 B64 B64)
/* B64quad represents three octets of binary data. */
[29]   B64final ::= B64finalquad | Padded16 | Padded8
[30]   B64finalquad ::= (B64 B64 B64 B64char)
/* B64finalquad represents three octets of binary data without trailing space. */
[31]   Padded16 ::= B64 B64 B16 '='
/* Padded16 represents a two-octet at the end of the data. */
[32]   Padded8 ::= B64 B04 '=' #x20? '='
/* Padded8 represents a single octet at the end of the data. */
[33]   B64 ::= B64char #x20?
[34]   B64char ::= [A-Za-z0-9+/]
[35]   B16 ::= B16char #x20?
[36]   B16char ::= [AEIMQUYcgkosw048]
/* Base64 characters whose bit-string value ends in '00' */
[37]   B04 ::= B04char #x20?
[38]   B04char ::= [AQgw]
/* Base64 characters whose bit-string value ends in '0000' */
The Base64Binary production is equivalent to the following regular expression.

((([A-Za-z0-9+/] ?){4})*(([A-Za-z0-9+/] ?){3}[A-Za-z0-9+/]|([A-Za-z0-9+/] ?){2}[AEIMQUYcgkosw048] ?=|[A-Za-z0-9+/] ?[AQgw] ?= ?=))?

Note that each '?' except the last is preceded by a single space character.

Note that this grammar requires the number of non-whitespace characters in the ·lexical representation· to be a multiple of four, and for equals signs to appear only at the end of the ·lexical representation·; literals which do not meet these constraints are not legal ·lexical representations· of base64Binary.

The ·lexical mapping· for base64Binary is as given in [RFC 2045] and [RFC 3548].

Note: The above definition of the ·lexical space· is more restrictive than that given in [RFC 2045] as regards whitespace — and less restrictive than [RFC 3548]. This is not an issue in practice.  Any string compatible with either RFC can occur in an element or attribute validated by this type, because the ·whiteSpace· facet of this type is fixed to collapse, which means that all leading and trailing whitespace will be stripped, and all internal whitespace collapsed to single space characters, before the above grammar is enforced. The possibility of ignoring whitespace in Base64 data is foreseen in clause 2.3 of [RFC 3548], but for the reasons given there this specification does not allow implementations to ignore non-whitespace characters which are not in the Base64 Alphabet.

The canonical ·lexical representation· of a base64Binary data value is the Base64 encoding of the value which matches the Canonical-base64Binary production in the following grammar:

Canonical representation of base64Binary
[39]   Canonical-base64Binary ::= CanonicalQuad* CanonicalPadded?
[40]   CanonicalQuad ::= B64char B64char B64char B64char
[41]   CanonicalPadded ::= B64char B64char B16char '=' | B64char B04char '=='

That is, the ·canonical representation· of a base64Binary value is the ·lexical representation· which maps to that value and contains no whitespace. The ·canonical mapping· for base64Binary is thus the encoding algorithm for Base64 data given in [RFC 2045] and [RFC 3548], with the proviso that no characters except those in the Base64 Alphabet are to be written out.

Note: For some values the ·canonical representation· defined above does not conform to [RFC 2045], which requires breaking with linefeeds at appropriate intervals. It does conform with [RFC 3548].

The length of a base64Binary value may be calculated from the ·lexical representation· by removing whitespace and padding characters and performing the calculation shown in the pseudo-code below:

lex2   := killwhitespace(lexform)    -- remove whitespace characters
lex3   := strip_equals(lex2)         -- strip padding characters at end
length := floor (length(lex3) * 3 / 4)         -- calculate length

Note on encoding:  [RFC 2045] and [RFC 3548] explicitly reference US-ASCII encoding.  However, decoding of base64Binary data in an XML entity is to be performed on the Unicode characters obtained after character encoding processing as specified by [XML].

3.3.16.3 Facets

The base64Binary datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from base64Binary may also specify values for the following ·constraining facets·:

The base64Binary datatype has the following values for its ·fundamental facets·:

3.3.17 anyURI

[Definition:]   anyURI represents an Internationalized Resource Identifier Reference (IRI).  An anyURI value can be absolute or relative, and may have an optional fragment identifier (i.e., it may be an IRI Reference).  This type should be used when the value fulfills the role of an IRI, as defined in [RFC 3987] or its successor(s) in the IETF Standards Track.

Note: IRIs may be used to locate resources or simply to identify them. In the case where they are used to locate resources using a URI, applications should use the mapping from anyURI values to URIs given by the reference escaping procedure defined in [LEIRI] and in Section 3.1 Mapping of IRIs to URIs of [RFC 3987] or its successor(s) in the IETF Standards Track.  This means that a wide range of internationalized resource identifiers can be specified when an anyURI is called for, and still be understood as URIs per [RFC 3986] and its successor(s).
3.3.17.1 Value Space

The value space of anyURI is the set of finite-length sequences of zero or more characters (as defined in [XML]) that ·match· the Char production from [XML].

3.3.17.2 Lexical Mapping

The ·lexical space· of anyURI is the set of finite-length sequences of zero or more characters (as defined in [XML]) that ·match· the Char production from [XML].

Note: For an anyURI value to be usable in practice as an IRI, the result of applying to it the algorithm defined in Section 3.1 of [RFC 3987] should be a string which is a legal URI according to [RFC 3986]. (This is true at the time this document is published; if in the future [RFC 3987] and [RFC 3986] are replaced by other specifications in the IETF Standards Track, the relevant constraints will be those imposed by those successor specifications.)
Each URI scheme imposes specialized syntax rules for URIs in that scheme, including restrictions on the syntax of allowed fragment identifiers. Because it is impractical for processors to check that a value is a context-appropriate URI reference, neither the syntactic constraints defined by the definitions of individual schemes nor the generic syntactic constraints defined by [RFC 3987] and [RFC 3986] and their successors are part of this datatype as defined here. Applications which depend on anyURI values being legal according to the rules of the relevant specifications should make arrangements to check values against the appropriate definitions of IRI, URI, and specific schemes.
Note: Spaces are, in principle, allowed in the ·lexical space· of anyURI, however, their use is highly discouraged (unless they are encoded by '%20').

The ·lexical mapping· for anyURI is the identity mapping.

Note: The definitions of URI in the current IETF specifications define certain URIs as equivalent to each other. Those equivalences are not part of this datatype as defined here: if two "equivalent" URIs or IRIs are different character sequences, they map to different values in this datatype.
3.3.17.3 Facets

The anyURI datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from anyURI may also specify values for the following ·constraining facets·:

The anyURI datatype has the following values for its ·fundamental facets·:

3.3.18 QName

[Definition:]   QName represents XML qualified names. The ·value space· of QName is the set of tuples {namespace name, local part}, where namespace name is an anyURI and local part is an NCName. The ·lexical space· of QName is the set of strings that ·match· the QName production of [Namespaces in XML].

It is ·implementation-defined· whether an implementation of this specification supports the QName production from [Namespaces in XML], or that from [Namespaces in XML 1.0], or both. See Dependencies on Other Specifications (§1.3).

The mapping from lexical space to value space for a particular QName ·literal· depends on the namespace bindings in scope where the literal occurs.

When QNames appear in an XML context, the bindings to be used in the ·lexical mapping· are those in the [in-scope namespaces] property of the relevant element. When this datatype is used in a non-XML host language, the host language must specify what namespace bindings are to be used.

The host language, whether XML-based or otherwise, may specify whether unqualified names are bound to the default namespace (if any) or not; the host language may also place this under user control. If the host language does not specify otherwise, unqualified names are bound to the default namespace.

Note: The default treatment of unqualified names parallels that specified in [Namespaces in XML] for element names (as opposed to that specified for attribute names).
Note: The mapping between ·literals· in the ·lexical space· and values in the ·value space· of QName depends on the set of namespace declarations in scope for the context in which QName is used. 
Because the lexical representations available for any value of type QName vary with context, no ·canonical representation· is defined for QName in this specification.
3.3.18.1 Facets

The QName datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from QName may also specify values for the following ·constraining facets·:

The QName datatype has the following values for its ·fundamental facets·:

3.3.19 NOTATION

[Definition:]  NOTATION represents the NOTATION attribute type from [XML]. The ·value space· of NOTATION is the set of QNames of notations declared in the current schema. The ·lexical space· of NOTATION is the set of all names of notations declared in the current schema (in the form of QNames).

Note: Because its ·value space· depends on the notion of a "current schema", as instantiated for example by [XSD 1.1 Part 1: Structures], the NOTATION datatype is unsuitable for use in other contexts which lack the notion of a current schema.

The lexical mapping rules for NOTATION are as given for QName in QName (§3.3.18).

Schema Component Constraint: enumeration facet value required for NOTATION
It is (with one exception) an ·error· for NOTATION to be used directly to validate a literal as described in Datatype Valid (§4.1.4): only datatypes ·derived· from NOTATION by specifying a value for ·enumeration· can be used to validate literals.
The exception is that in the ·derivation· of a new type the ·literals· used to enumerate the allowed values may be (and in the context of [XSD 1.1 Part 1: Structures] will be) validated directly against NOTATION; this amounts to verifying that the value is a QName and that the QName is the name of a NOTATION declared in the current schema.

For compatibility (see Terminology (§1.6)) NOTATION should be used only on attributes and should only be used in schemas with no target namespace.

Note: Because the lexical representations available for any given value of NOTATION vary with context, this specification defines no ·canonical representation· for NOTATION values.
3.3.19.1 Facets

The NOTATION datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from NOTATION may also specify values for the following ·constraining facets·:

The NOTATION datatype has the following values for its ·fundamental facets·:

The use of ·length·, ·minLength· and ·maxLength· on NOTATION or datatypes ·derived· from NOTATION is deprecated.  Future versions of this specification may remove these facets for this datatype.

previous sub-section 3.4 Other Built-in Datatypes

        3.4.1 normalizedString
            3.4.1.1 Facets
            3.4.1.2 Derived datatypes
        3.4.2 token
            3.4.2.1 Facets
            3.4.2.2 Derived datatypes
        3.4.3 language
            3.4.3.1 Facets
        3.4.4 NMTOKEN
            3.4.4.1 Facets
            3.4.4.2 Related datatypes
        3.4.5 NMTOKENS
            3.4.5.1 Facets
        3.4.6 Name
            3.4.6.1 Facets
            3.4.6.2 Derived datatypes
        3.4.7 NCName
            3.4.7.1 Facets
            3.4.7.2 Derived datatypes
        3.4.8 ID
            3.4.8.1 Facets
        3.4.9 IDREF
            3.4.9.1 Facets
            3.4.9.2 Related datatypes
        3.4.10 IDREFS
            3.4.10.1 Facets
        3.4.11 ENTITY
            3.4.11.1 Facets
            3.4.11.2 Related datatypes
        3.4.12 ENTITIES
            3.4.12.1 Facets
        3.4.13 integer
            3.4.13.1 Lexical representation
            3.4.13.2 Canonical representation
            3.4.13.3 Facets
            3.4.13.4 Derived datatypes
        3.4.14 nonPositiveInteger
            3.4.14.1 Lexical representation
            3.4.14.2 Canonical representation
            3.4.14.3 Facets
            3.4.14.4 Derived datatypes
        3.4.15 negativeInteger
            3.4.15.1 Lexical representation
            3.4.15.2 Canonical representation
            3.4.15.3 Facets
        3.4.16 long
            3.4.16.1 Lexical Representation
            3.4.16.2 Canonical Representation
            3.4.16.3 Facets
            3.4.16.4 Derived datatypes
        3.4.17 int
            3.4.17.1 Lexical Representation
            3.4.17.2 Canonical representation
            3.4.17.3 Facets
            3.4.17.4 Derived datatypes
        3.4.18 short
            3.4.18.1 Lexical representation
            3.4.18.2 Canonical representation
            3.4.18.3 Facets
            3.4.18.4 Derived datatypes
        3.4.19 byte
            3.4.19.1 Lexical representation
            3.4.19.2 Canonical representation
            3.4.19.3 Facets
        3.4.20 nonNegativeInteger
            3.4.20.1 Lexical representation
            3.4.20.2 Canonical representation
            3.4.20.3 Facets
            3.4.20.4 Derived datatypes
        3.4.21 unsignedLong
            3.4.21.1 Lexical representation
            3.4.21.2 Canonical representation
            3.4.21.3 Facets
            3.4.21.4 Derived datatypes
        3.4.22 unsignedInt
            3.4.22.1 Lexical representation
            3.4.22.2 Canonical representation
            3.4.22.3 Facets
            3.4.22.4 Derived datatypes
        3.4.23 unsignedShort
            3.4.23.1 Lexical representation
            3.4.23.2 Canonical representation
            3.4.23.3 Facets
            3.4.23.4 Derived datatypes
        3.4.24 unsignedByte
            3.4.24.1 Lexical representation
            3.4.24.2 Canonical representation
            3.4.24.3 Facets
        3.4.25 positiveInteger
            3.4.25.1 Lexical representation
            3.4.25.2 Canonical representation
            3.4.25.3 Facets
        3.4.26 yearMonthDuration
            3.4.26.1 The Lexical Mapping
            3.4.26.2 Facets
        3.4.27 dayTimeDuration
            3.4.27.1 The Lexical Space
            3.4.27.2 Facets
        3.4.28 dateTimeStamp
            3.4.28.1 The Lexical Space
            3.4.28.2 Facets

This section gives conceptual definitions for all ·built-in· ·ordinary· datatypes defined by this specification. The XML representation used to define ·ordinary· datatypes (whether ·built-in· or ·user-defined·) is given in XML Representation of Simple Type Definition Schema Components (§4.1.2) and the complete definitions of the ·built-in· ·ordinary· datatypes are provided in the appendix Schema for Schema Documents (Datatypes) (normative) (§A).

3.4.1 normalizedString

[Definition:]   normalizedString represents white space normalized strings.  The ·value space· of normalizedString is the set of strings that do not contain the carriage return (#xD), line feed (#xA) nor tab (#x9) characters.  The ·lexical space· of normalizedString is the set of strings that do not contain the carriage return (#xD), line feed (#xA) nor tab (#x9) characters.  The ·base type· of normalizedString is string.

3.4.1.1 Facets

The normalizedString datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from normalizedString may also specify values for the following ·constraining facets·:

The normalizedString datatype has the following values for its ·fundamental facets·:

3.4.1.2 Derived datatypes

The following ·built-in· datatype is ·derived· from normalizedString

3.4.2 token

[Definition:]   token represents tokenized strings. The ·value space· of token is the set of strings that do not contain the carriage return (#xD), line feed (#xA) nor tab (#x9) characters, that have no leading or trailing spaces (#x20) and that have no internal sequences of two or more spaces. The ·lexical space· of token is the set of strings that do not contain the carriage return (#xD), line feed (#xA) nor tab (#x9) characters, that have no leading or trailing spaces (#x20) and that have no internal sequences of two or more spaces. The ·base type· of token is normalizedString.

3.4.2.1 Facets

The token datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from token may also specify values for the following ·constraining facets·:

The token datatype has the following values for its ·fundamental facets·:

3.4.2.2 Derived datatypes

The following ·built-in· datatypes are ·derived· from token

3.4.3 language

[Definition:]  language represents formal natural language identifiers, as defined by [BCP 47] (currently represented by [RFC 4646] and [RFC 4647]) or its successor(s). The ·value space· and ·lexical space· of language are the set of all strings that conform to the pattern

[a-zA-Z]{1,8}(-[a-zA-Z0-9]{1,8})*

This is the set of strings accepted by the grammar given in [RFC 3066], which is now obsolete; the current specification of language codes is more restrictive.  The ·base type· of language is token.
Note: The regular expression above provides the only normative constraint on the lexical and value spaces of this type. The additional constraints imposed on language identifiers by [BCP 47] and its successor(s), and in particular their requirement that language codes be registered with IANA or ISO if not given in ISO 639, are not part of this datatype as defined here.
Note: [BCP 47] specifies that language codes "are to be treated as case insensitive; there exist conventions for capitalization of some of the subtags, but these MUST NOT be taken to carry meaning." Since the language datatype is derived from string, it inherits from string a one-to-one mapping from lexical representations to values. The literals 'MN' and 'mn' (for Mongolian) therefore correspond to distinct values and have distinct canonical forms. Users of this specification should be aware of this fact, the consequence of which is that the case-insensitive treatment of language values prescribed by [BCP 47] does not follow from the definition of this datatype given here; applications which require case-insensitivity should make appropriate adjustments.
Note: The empty string is not a member of the ·value space· of language. Some constructs which normally take language codes as their values, however, also allow the empty string. The attribute xml:lang defined by [XML] is one example; there, the empty string overrides a value which would otherwise be inherited, but without specifying a new value.
One way to define the desired set of possible values is illustrated by the schema document for the XML namespace at http://www.w3.org/2001/xml.xsd, which defines the attribute xml:lang as having a type which is a union of language and an anonymous type whose only value is the empty string:
 <xs:attribute name="lang">
   <xs:annotation>
     <xs:documentation>
       See RFC 3066 at http://www.ietf.org/rfc/rfc3066.txt 
       and the IANA registry at 
       http://www.iana.org/assignments/lang-tag-apps.htm for
       further information.

       The union allows for the 'un-declaration' of xml:lang with
       the empty string.
     </xs:documentation>
   </xs:annotation>
   <xs:simpleType>
     <xs:union memberTypes="xs:language">
       <xs:simpleType>    
         <xs:restriction base="xs:string">
           <xs:enumeration value=""/>
         </xs:restriction>
       </xs:simpleType>
     </xs:union>
   </xs:simpleType>
 </xs:attribute>
3.4.3.1 Facets

The language datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from language may also specify values for the following ·constraining facets·:

The language datatype has the following values for its ·fundamental facets·:

3.4.4 NMTOKEN

[Definition:]   NMTOKEN represents the NMTOKEN attribute type from [XML]. The ·value space· of NMTOKEN is the set of tokens that ·match· the Nmtoken production in [XML]. The ·lexical space· of NMTOKEN is the set of strings that ·match· the Nmtoken production in [XML].  The ·base type· of NMTOKEN is token.

It is ·implementation-defined· whether an implementation of this specification supports the NMTOKEN production from [XML], or that from [XML 1.0], or both. See Dependencies on Other Specifications (§1.3).

For compatibility (see Terminology (§1.6) NMTOKEN should be used only on attributes.

3.4.4.1 Facets

The NMTOKEN datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from NMTOKEN may also specify values for the following ·constraining facets·:

The NMTOKEN datatype has the following values for its ·fundamental facets·:

3.4.4.2 Related datatypes

The following ·built-in· datatype is ·constructed· from NMTOKEN

3.4.5 NMTOKENS

[Definition:]  NMTOKENS represents the NMTOKENS attribute type from [XML]. The ·value space· of NMTOKENS is the set of finite, non-zero-length sequences of ·NMTOKEN·s.  The ·lexical space· of NMTOKENS is the set of space-separated lists of tokens, of which each token is in the ·lexical space· of NMTOKEN.  The ·item type· of NMTOKENS is NMTOKEN. NMTOKENS is derived from ·anySimpleType· in two steps: an anonymous list type is defined, whose ·item type· is NMTOKEN; this is the ·base type· of NMTOKENS, which restricts its value space to lists with at least one item.

For compatibility (see Terminology (§1.6)) NMTOKENS should be used only on attributes.

3.4.5.1 Facets

The NMTOKENS datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from NMTOKENS may also specify values for the following ·constraining facets·:

The NMTOKENS datatype has the following values for its ·fundamental facets·:

3.4.6 Name

[Definition:]   Name represents XML Names. The ·value space· of Name is the set of all strings which ·match· the Name production of [XML].  The ·lexical space· of Name is the set of all strings which ·match· the Name production of [XML]. The ·base type· of Name is token.

It is ·implementation-defined· whether an implementation of this specification supports the Name production from [XML], or that from [XML 1.0], or both. See Dependencies on Other Specifications (§1.3).

3.4.6.1 Facets

The Name datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from Name may also specify values for the following ·constraining facets·:

The Name datatype has the following values for its ·fundamental facets·:

3.4.6.2 Derived datatypes

The following ·built-in· datatype is ·derived· from Name

3.4.7 NCName

[Definition:]   NCName represents XML "non-colonized" Names.  The ·value space· of NCName is the set of all strings which ·match· the NCName production of [Namespaces in XML].  The ·lexical space· of NCName is the set of all strings which ·match· the NCName production of [Namespaces in XML].  The ·base type· of NCName is Name.

It is ·implementation-defined· whether an implementation of this specification supports the NCName production from [Namespaces in XML], or that from [Namespaces in XML 1.0], or both. See Dependencies on Other Specifications (§1.3).

3.4.7.1 Facets

The NCName datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from NCName may also specify values for the following ·constraining facets·:

The NCName datatype has the following values for its ·fundamental facets·:

3.4.7.2 Derived datatypes

The following ·built-in· datatypes are ·derived· from NCName

3.4.8 ID

[Definition:]  ID represents the ID attribute type from [XML].  The ·value space· of ID is the set of all strings that ·match· the NCName production in [Namespaces in XML].  The ·lexical space· of ID is the set of all strings that ·match· the NCName production in [Namespaces in XML]. The ·base type· of ID is NCName.

Note: It is ·implementation-defined· whether an implementation of this specification supports the NCName production from [Namespaces in XML], or that from [Namespaces in XML 1.0], or both. See Dependencies on Other Specifications (§1.3).

For compatibility (see Terminology (§1.6)), ID should be used only on attributes.

Note: Uniqueness of items validated as ID is not part of this datatype as defined here. When this specification is used in conjunction with [XSD 1.1 Part 1: Structures], uniqueness is enforced at a different level, not as part of datatype validity; see Validation Rule: Validation Root Valid (ID/IDREF) in [XSD 1.1 Part 1: Structures].
3.4.8.1 Facets

The ID datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from ID may also specify values for the following ·constraining facets·:

The ID datatype has the following values for its ·fundamental facets·:

3.4.9 IDREF

[Definition:]   IDREF represents the IDREF attribute type from [XML].  The ·value space· of IDREF is the set of all strings that ·match· the NCName production in [Namespaces in XML].  The ·lexical space· of IDREF is the set of strings that ·match· the NCName production in [Namespaces in XML]. The ·base type· of IDREF is NCName.

Note: It is ·implementation-defined· whether an implementation of this specification supports the NCName production from [Namespaces in XML], or that from [Namespaces in XML 1.0], or both. See Dependencies on Other Specifications (§1.3).

For compatibility (see Terminology (§1.6)) this datatype should be used only on attributes.

Note: Existence of referents for items validated as IDREF is not part of this datatype as defined here. When this specification is used in conjunction with [XSD 1.1 Part 1: Structures], referential integrity is enforced at a different level, not as part of datatype validity; see Validation Rule: Validation Root Valid (ID/IDREF) in [XSD 1.1 Part 1: Structures].
3.4.9.1 Facets

The IDREF datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from IDREF may also specify values for the following ·constraining facets·:

The IDREF datatype has the following values for its ·fundamental facets·:

3.4.9.2 Related datatypes

The following ·built-in· datatype is ·constructed· from IDREF

3.4.10 IDREFS

[Definition:]   IDREFS represents the IDREFS attribute type from [XML].  The ·value space· of IDREFS is the set of finite, non-zero-length sequences of IDREFs. The ·lexical space· of IDREFS is the set of space-separated lists of tokens, of which each token is in the ·lexical space· of IDREF.  The ·item type· of IDREFS is IDREF. IDREFS is derived from ·anySimpleType· in two steps: an anonymous list type is defined, whose ·item type· is IDREF; this is the ·base type· of IDREFS, which restricts its value space to lists with at least one item.

For compatibility (see Terminology (§1.6)) IDREFS should be used only on attributes.

Note: Existence of referents for items validated as IDREFS is not part of this datatype as defined here. When this specification is used in conjunction with [XSD 1.1 Part 1: Structures], referential integrity is enforced at a different level, not as part of datatype validity; see Validation Rule: Validation Root Valid (ID/IDREF) in [XSD 1.1 Part 1: Structures].
3.4.10.1 Facets

The IDREFS datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from IDREFS may also specify values for the following ·constraining facets·:

The IDREFS datatype has the following values for its ·fundamental facets·:

3.4.11 ENTITY

[Definition:]   ENTITY represents the ENTITY attribute type from [XML].  The ·value space· of ENTITY is the set of all strings that ·match· the NCName production in [Namespaces in XML] and have been declared as an unparsed entity in a document type definition. The ·lexical space· of ENTITY is the set of all strings that ·match· the NCName production in [Namespaces in XML]. The ·base type· of ENTITY is NCName.

Note: It is ·implementation-defined· whether an implementation of this specification supports the NCName production from [Namespaces in XML], or that from [Namespaces in XML 1.0], or both. See Dependencies on Other Specifications (§1.3).
Note: The ·value space· of ENTITY is scoped to a specific instance document.

For compatibility (see Terminology (§1.6)) ENTITY should be used only on attributes.

3.4.11.1 Facets

The ENTITY datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from ENTITY may also specify values for the following ·constraining facets·:

The ENTITY datatype has the following values for its ·fundamental facets·:

3.4.11.2 Related datatypes

The following ·built-in· datatype is ·constructed· from ENTITY

3.4.12 ENTITIES

[Definition:]  ENTITIES represents the ENTITIES attribute type from [XML].  The ·value space· of ENTITIES is the set of finite, non-zero-length sequences of ·ENTITY· values that have been declared as unparsed entities in a document type definition.  The ·lexical space· of ENTITIES is the set of space-separated lists of tokens, of which each token is in the ·lexical space· of ENTITY.  The ·item type· of ENTITIES is ENTITY. ENTITIES is derived from ·anySimpleType· in two steps: an anonymous list type is defined, whose ·item type· is ENTITY; this is the ·base type· of ENTITIES, which restricts its value space to lists with at least one item.

Note: The ·value space· of ENTITIES is scoped to a specific instance document.

For compatibility (see Terminology (§1.6)) ENTITIES should be used only on attributes.

3.4.12.1 Facets

The ENTITIES datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from ENTITIES may also specify values for the following ·constraining facets·:

The ENTITIES datatype has the following values for its ·fundamental facets·:

3.4.13 integer

[Definition:]   integer is ·derived· from decimal by fixing the value of ·fractionDigits· to be 0 and disallowing the trailing decimal point.  This results in the standard mathematical concept of the integer numbers.  The ·value space· of integer is the infinite set {...,-2,-1,0,1,2,...}.  The ·base type· of integer is decimal.

3.4.13.1 Lexical representation

integer has a lexical representation consisting of a finite-length sequence of one or more decimal digits (#x30-#x39) with an optional leading sign.  If the sign is omitted, "+" is assumed.  For example: -1, 0, 12678967543233, +100000.

3.4.13.2 Canonical representation

The ·canonical representation· for integer is defined by prohibiting certain options from the Lexical representation (§3.4.13.1).  Specifically, the preceding optional "+" sign is prohibited and leading zeroes are prohibited.

3.4.13.3 Facets

The integer datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The integer datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from integer may also specify values for the following ·constraining facets·:

The integer datatype has the following values for its ·fundamental facets·:

3.4.13.4 Derived datatypes

The following ·built-in· datatypes are ·derived· from integer

3.4.14 nonPositiveInteger

[Definition:]   nonPositiveInteger is ·derived· from integer by setting the value of ·maxInclusive· to be 0.  This results in the standard mathematical concept of the non-positive integers. The ·value space· of nonPositiveInteger is the infinite set {...,-2,-1,0}.  The ·base type· of nonPositiveInteger is integer.

3.4.14.1 Lexical representation

nonPositiveInteger has a lexical representation consisting of an optional preceding sign followed by a non-empty finite-length sequence of decimal digits (#x30-#x39).  The sign may be "+" or may be omitted only for lexical forms denoting zero; in all other lexical forms, the negative sign ('-') must be present.  For example: -1, 0, -12678967543233, -100000.

3.4.14.2 Canonical representation

The ·canonical representation· for nonPositiveInteger is defined by prohibiting certain options from the Lexical representation (§3.4.14.1).  In the canonical form for zero, the sign must be omitted.  Leading zeroes are prohibited.

3.4.14.3 Facets

The nonPositiveInteger datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The nonPositiveInteger datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from nonPositiveInteger may also specify values for the following ·constraining facets·:

The nonPositiveInteger datatype has the following values for its ·fundamental facets·:

3.4.14.4 Derived datatypes

The following ·built-in· datatype is ·derived· from nonPositiveInteger

3.4.15 negativeInteger

[Definition:]   negativeInteger is ·derived· from nonPositiveInteger by setting the value of ·maxInclusive· to be -1.  This results in the standard mathematical concept of the negative integers.  The ·value space· of negativeInteger is the infinite set {...,-2,-1}.  The ·base type· of negativeInteger is nonPositiveInteger.

3.4.15.1 Lexical representation

negativeInteger has a lexical representation consisting of a negative sign ('-') followed by a non-empty finite-length sequence of decimal digits (#x30-#x39), at least one of which must be a digit other than '0'.  For example: -1, -12678967543233, -100000.

3.4.15.2 Canonical representation

The ·canonical representation· for negativeInteger is defined by prohibiting certain options from the Lexical representation (§3.4.15.1).  Specifically, leading zeroes are prohibited.

3.4.15.3 Facets

The negativeInteger datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The negativeInteger datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from negativeInteger may also specify values for the following ·constraining facets·:

The negativeInteger datatype has the following values for its ·fundamental facets·:

3.4.16 long

[Definition:]   long is ·derived· from integer by setting the value of ·maxInclusive· to be 9223372036854775807 and ·minInclusive· to be -9223372036854775808. The ·base type· of long is integer.

3.4.16.1 Lexical Representation

long has a lexical representation consisting of an optional sign followed by a non-empty finite-length sequence of decimal digits (#x30-#x39).  If the sign is omitted, "+" is assumed.  For example: -1, 0, 12678967543233, +100000.

3.4.16.2 Canonical Representation

The ·canonical representation· for long is defined by prohibiting certain options from the Lexical Representation (§3.4.16.1).  Specifically, the the optional "+" sign is prohibited and leading zeroes are prohibited.

3.4.16.3 Facets

The long datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The long datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from long may also specify values for the following ·constraining facets·:

The long datatype has the following values for its ·fundamental facets·:

3.4.16.4 Derived datatypes

The following ·built-in· datatype is ·derived· from long

3.4.17 int

[Definition:]   int is ·derived· from long by setting the value of ·maxInclusive· to be 2147483647 and ·minInclusive· to be -2147483648.  The ·base type· of int is long.

3.4.17.1 Lexical Representation

int has a lexical representation consisting of an optional sign followed by a non-empty finite-length sequence of decimal digits (#x30-#x39).  If the sign is omitted, "+" is assumed. For example: -1, 0, 126789675, +100000.

3.4.17.2 Canonical representation

The ·canonical representation· for int is defined by prohibiting certain options from the Lexical Representation (§3.4.17.1).  Specifically, the the optional "+" sign is prohibited and leading zeroes are prohibited.

3.4.17.3 Facets

The int datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The int datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from int may also specify values for the following ·constraining facets·:

The int datatype has the following values for its ·fundamental facets·:

3.4.17.4 Derived datatypes

The following ·built-in· datatype is ·derived· from int

3.4.18 short

[Definition:]   short is ·derived· from int by setting the value of ·maxInclusive· to be 32767 and ·minInclusive· to be -32768.  The ·base type· of short is int.

3.4.18.1 Lexical representation

short has a lexical representation consisting of an optional sign followed by a non-empty finite-length sequence of decimal digits (#x30-#x39).  If the sign is omitted, "+" is assumed. For example: -1, 0, 12678, +10000.

3.4.18.2 Canonical representation

The ·canonical representation· for short is defined by prohibiting certain options from the Lexical representation (§3.4.18.1).  Specifically, the the optional "+" sign is prohibited and leading zeroes are prohibited.

3.4.18.3 Facets

The short datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The short datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from short may also specify values for the following ·constraining facets·:

The short datatype has the following values for its ·fundamental facets·:

3.4.18.4 Derived datatypes

The following ·built-in· datatype is ·derived· from short

3.4.19 byte

[Definition:]   byte is ·derived· from short by setting the value of ·maxInclusive· to be 127 and ·minInclusive· to be -128. The ·base type· of byte is short.

3.4.19.1 Lexical representation

byte has a lexical representation consisting of an optional sign followed by a non-empty finite-length sequence of decimal digits (#x30-#x39).  If the sign is omitted, "+" is assumed. For example: -1, 0, 126, +100.

3.4.19.2 Canonical representation

The ·canonical representation· for byte is defined by prohibiting certain options from the Lexical representation (§3.4.19.1).  Specifically, the the optional "+" sign is prohibited and leading zeroes are prohibited.

3.4.19.3 Facets

The byte datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The byte datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from byte may also specify values for the following ·constraining facets·:

The byte datatype has the following values for its ·fundamental facets·:

3.4.20 nonNegativeInteger

[Definition:]   nonNegativeInteger is ·derived· from integer by setting the value of ·minInclusive· to be 0.  This results in the standard mathematical concept of the non-negative integers. The ·value space· of nonNegativeInteger is the infinite set {0,1,2,...}.  The ·base type· of nonNegativeInteger is integer.

3.4.20.1 Lexical representation

nonNegativeInteger has a lexical representation consisting of an optional sign followed by a non-empty finite-length sequence of decimal digits (#x30-#x39).  If the sign is omitted, the positive sign ('+') is assumed. If the sign is present, it must be "+" except for lexical forms denoting zero, which may be preceded by a positive ('+') or a negative ('-') sign. For example: 1, 0, 12678967543233, +100000.

3.4.20.2 Canonical representation

The ·canonical representation· for nonNegativeInteger is defined by prohibiting certain options from the Lexical representation (§3.4.20.1).  Specifically, the the optional "+" sign is prohibited and leading zeroes are prohibited.

3.4.20.3 Facets

The nonNegativeInteger datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The nonNegativeInteger datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from nonNegativeInteger may also specify values for the following ·constraining facets·:

The nonNegativeInteger datatype has the following values for its ·fundamental facets·:

3.4.20.4 Derived datatypes

The following ·built-in· datatypes are ·derived· from nonNegativeInteger

3.4.21 unsignedLong

[Definition:]   unsignedLong is ·derived· from nonNegativeInteger by setting the value of ·maxInclusive· to be 18446744073709551615.  The ·base type· of unsignedLong is nonNegativeInteger.

3.4.21.1 Lexical representation

unsignedLong has a lexical representation consisting of an optional sign followed by a non-empty finite-length sequence of decimal digits (#x30-#x39).  If the sign is omitted, the positive sign ('+') is assumed.  If the sign is present, it must be '+' except for lexical forms denoting zero, which may be preceded by a positive ('+') or a negative ('-') sign. For example: 0, 12678967543233, 100000.

3.4.21.2 Canonical representation

The ·canonical representation· for unsignedLong is defined by prohibiting certain options from the Lexical representation (§3.4.21.1).  Specifically, leading zeroes are prohibited.

3.4.21.3 Facets

The unsignedLong datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The unsignedLong datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from unsignedLong may also specify values for the following ·constraining facets·:

The unsignedLong datatype has the following values for its ·fundamental facets·:

3.4.21.4 Derived datatypes

The following ·built-in· datatype is ·derived· from unsignedLong

3.4.22 unsignedInt

[Definition:]   unsignedInt is ·derived· from unsignedLong by setting the value of ·maxInclusive· to be 4294967295.  The ·base type· of unsignedInt is unsignedLong.

3.4.22.1 Lexical representation

unsignedInt has a lexical representation consisting of an optional sign followed by a non-empty finite-length sequence of decimal digits (#x30-#x39).  If the sign is omitted, the positive sign ('+') is assumed.  If the sign is present, it must be '+' except for lexical forms denoting zero, which may be preceded by a positive ('+') or a negative ('-') sign. For example: 0, 1267896754, 100000.

3.4.22.2 Canonical representation

The ·canonical representation· for unsignedInt is defined by prohibiting certain options from the Lexical representation (§3.4.22.1).  Specifically, leading zeroes are prohibited.

3.4.22.3 Facets

The unsignedInt datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The unsignedInt datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from unsignedInt may also specify values for the following ·constraining facets·:

The unsignedInt datatype has the following values for its ·fundamental facets·:

3.4.22.4 Derived datatypes

The following ·built-in· datatype is ·derived· from unsignedInt

3.4.23 unsignedShort

[Definition:]   unsignedShort is ·derived· from unsignedInt by setting the value of ·maxInclusive· to be 65535.  The ·base type· of unsignedShort is unsignedInt.

3.4.23.1 Lexical representation

unsignedShort has a lexical representation consisting of an optional sign followed by a non-empty finite-length sequence of decimal digits (#x30-#x39). If the sign is omitted, the positive sign ('+') is assumed.  If the sign is present, it must be '+' except for lexical forms denoting zero, which may be preceded by a positive ('+') or a negative ('-') sign.  For example: 0, 12678, 10000.

3.4.23.2 Canonical representation

The ·canonical representation· for unsignedShort is defined by prohibiting certain options from the Lexical representation (§3.4.23.1).  Specifically, the leading zeroes are prohibited.

3.4.23.3 Facets

The unsignedShort datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The unsignedShort datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from unsignedShort may also specify values for the following ·constraining facets·:

The unsignedShort datatype has the following values for its ·fundamental facets·:

3.4.23.4 Derived datatypes

The following ·built-in· datatype is ·derived· from unsignedShort

3.4.24 unsignedByte

[Definition:]   unsignedByte is ·derived· from unsignedShort by setting the value of ·maxInclusive· to be 255.  The ·base type· of unsignedByte is unsignedShort.

3.4.24.1 Lexical representation

unsignedByte has a lexical representation consisting of an optional sign followed by a non-empty finite-length sequence of decimal digits (#x30-#x39). If the sign is omitted, the positive sign ('+') is assumed.  If the sign is present, it must be '+' except for lexical forms denoting zero, which may be preceded by a positive ('+') or a negative ('-') sign.  For example: 0, 126, 100.

3.4.24.2 Canonical representation

The ·canonical representation· for unsignedByte is defined by prohibiting certain options from the Lexical representation (§3.4.24.1).  Specifically, leading zeroes are prohibited.

3.4.24.3 Facets

The unsignedByte datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The unsignedByte datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from unsignedByte may also specify values for the following ·constraining facets·:

The unsignedByte datatype has the following values for its ·fundamental facets·:

3.4.25 positiveInteger

[Definition:]   positiveInteger is ·derived· from nonNegativeInteger by setting the value of ·minInclusive· to be 1.  This results in the standard mathematical concept of the positive integer numbers.  The ·value space· of positiveInteger is the infinite set {1,2,...}.  The ·base type· of positiveInteger is nonNegativeInteger.

3.4.25.1 Lexical representation

positiveInteger has a lexical representation consisting of an optional positive sign ('+') followed by a non-empty finite-length sequence of decimal digits (#x30-#x39), at least one of which must be a digit other than '0'.  For example: 1, 12678967543233, +100000.

3.4.25.2 Canonical representation

The ·canonical representation· for positiveInteger is defined by prohibiting certain options from the Lexical representation (§3.4.25.1).  Specifically, the optional "+" sign is prohibited and leading zeroes are prohibited.

3.4.25.3 Facets

The positiveInteger datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The positiveInteger datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from positiveInteger may also specify values for the following ·constraining facets·:

The positiveInteger datatype has the following values for its ·fundamental facets·:

3.4.26 yearMonthDuration

[Definition:]   yearMonthDuration is a datatype ·derived· from duration by restricting its ·lexical representations· to instances of yearMonthDurationLexicalRep.  The ·value space· of yearMonthDuration is therefore that of duration restricted to those whose ·seconds· property is 0.  This results in a duration datatype which is totally ordered.

Note: The always-zero ·seconds· is formally retained in order that yearMonthDuration's (abstract) value space truly be a subset of that of duration  An obvious implementation optimization is to ignore the zero and implement yearMonthDuration values simply as integer values.
3.4.26.1 The yearMonthDuration Lexical Mapping
The lexical space is reduced from that of duration by disallowing duDayFrag and duTimeFrag fragments in the ·lexical representations·.
The yearMonthDuration Lexical Representation
[42]   yearMonthDurationLexicalRep ::= '-'? 'PduYearMonthFrag

The lexical space of yearMonthDuration consists of strings which match the regular expression '-?P((([0-9]+Y)([0-9]+M)?)|([0-9]+M))' or the expression '-?P[0-9]+(Y([0-9]+M)?|M)', but the formal definition of yearMonthDuration uses a simpler regular expression in its ·pattern· facet: '[^DT]*'. This pattern matches only strings of characters which contain no 'D' and no 'T', thus restricting the ·lexical space· of duration to strings with no day, hour, minute, or seconds fields.

The ·canonical mapping· is that of duration restricted in its range to the ·lexical space· (which reduces its domain to omit any values not in the yearMonthDuration value space).

Note: The yearMonthDuration value whose ·months· and ·seconds· are both zero has no ·canonical representation· in this datatype since its ·canonical representation· in duration ('PT0S') is not in the ·lexical space· of yearMonthDuration.
3.4.26.2 Facets

The yearMonthDuration datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The yearMonthDuration datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from yearMonthDuration may also specify values for the following ·constraining facets·:

The yearMonthDuration datatype has the following values for its ·fundamental facets·:

Note: The ordered facet has the value partial even though the datatype is in fact totally ordered, because (as explained in ordered (§4.2.1)), the value of that facet is unchanged by derivation.

3.4.27 dayTimeDuration

[Definition:]   dayTimeDuration is a datatype ·derived· from duration by restricting its ·lexical representations· to instances of dayTimeDurationLexicalRep. The ·value space· of dayTimeDuration is therefore that of duration restricted to those whose ·months· property is 0.  This results in a duration datatype which is totally ordered.

3.4.27.1 The dayTimeDuration Lexical Space

The lexical space is reduced from that of duration by disallowing duYearFrag and duMonthFrag fragments in the ·lexical representations·.

The dayTimeDuration Lexical Representation
[43]   dayTimeDurationLexicalRep ::= '-'? 'PduDayTimeFrag

The lexical space of dayTimeDuration consists of strings in the ·lexical space· of duration which match the regular expression '[^YM]*[DT].*'; this pattern eliminates all durations with year or month fields, leaving only those with day, hour, minutes, and/or seconds fields.

The ·canonical mapping· is that of duration restricted in its range to the ·lexical space· (which reduces its domain to omit any values not in the dayTimeDuration value space).

3.4.27.2 Facets

The dayTimeDuration datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

The dayTimeDuration datatype has the following ·constraining facets· with the values shown; these facets may be specified in the derivation of new types, if the value given is at least as restrictive as the one shown:

Datatypes derived by restriction from dayTimeDuration may also specify values for the following ·constraining facets·:

The dayTimeDuration datatype has the following values for its ·fundamental facets·:

Note: The ordered facet has the value partial even though the datatype is in fact totally ordered, because (as explained in ordered (§4.2.1)), the value of that facet is unchanged by derivation.

3.4.28 dateTimeStamp

[Definition:]   The dateTimeStamp datatype is ·derived· from dateTime by giving the value required to its explicitTimezone facet. The result is that all values of dateTimeStamp are required to have explicit time zone offsets and the datatype is totally ordered.

3.4.28.1 The dateTimeStamp Lexical Space

As a consequence of requiring an explicit time zone offset, the lexical space of dateTimeStamp is reduced from that of dateTime by requiring a timezoneFrag fragment in the ·lexical representations·.

The dateTimeStamp Lexical Representation
[44]   dateTimeStampLexicalRep ::= yearFrag '-monthFrag '-dayFrag 'T' ((hourFrag ':minuteFrag ':secondFrag) | endOfDayFrag) timezoneFrag   Constraint:  Day-of-month Representations
Note: For details of the Day-of-month Representations (§3.3.7.2) constraint, see dateTime, from which the constraint is inherited.

In other words, the lexical space of dateTimeStamp consists of strings which are in the ·lexical space· of dateTime and which also match the regular expression '.*(Z|(\+|-)[0-9][0-9]:[0-9][0-9])'.

The ·lexical mapping· is that of dateTime restricted to the dateTimeStamp lexical space.

The ·canonical mapping· is that of dateTime restricted to the dateTimeStamp value space.

3.4.28.2 Facets

The dateTimeStamp datatype and all datatypes derived from it by restriction have the following ·constraining facets· with fixed values; these facets must not be changed from the values shown:

Datatypes derived by restriction from dateTimeStamp may also specify values for the following ·constraining facets·:

The dateTimeStamp datatype has the following values for its ·fundamental facets·:

Note: The ordered facet has the value partial even though the datatype is in fact totally ordered, because (as explained in ordered (§4.2.1)), the value of that facet is unchanged by derivation.

4 Datatype components

The preceding sections of this specification have described datatypes in a way largely independent of their use in the particular context of schema-aware processing as defined in [XSD 1.1 Part 1: Structures].

This section presents the mechanisms necessary to integrate datatypes into the context of [XSD 1.1 Part 1: Structures], mostly in terms of the schema component abstraction introduced there. The account of datatypes given in this specification is also intended to be useful in other contexts. Any specification or other formal system intending to use datatypes as defined above, particularly if definition of new datatypes via facet-based restriction is envisaged, will need to provide analogous mechanisms for some, but not necessarily all, of what follows below. For example, the {target namespace} and {final} properties are required because of particular aspects of [XSD 1.1 Part 1: Structures] which are not in principle necessary for the use of datatypes as defined here.

The following sections provide full details on the properties and significance of each kind of schema component involved in datatype definitions. For each property, the kinds of values it is allowed to have is specified.  Any property not identified as optional is required to be present; optional properties which are not present have absent as their value. Any property identified as a having a set, subset or ·list· value may have an empty value unless this is explicitly ruled out: this is not the same as absent. Any property value identified as a superset or a subset of some set may be equal to that set, unless a proper superset or subset is explicitly called for.

For more information on the notion of schema components, see Schema Component Details of [XSD 1.1 Part 1: Structures].

[Definition:]  A component may be referred to as the owner of its properties, and of the values of those properties.

next sub-section4.1 Simple Type Definition

Simple Type Definitions provide for:

  • In the case of ·primitive· datatypes, identifying a datatype with its definition in this specification.
  • In the case of ·constructed· datatypes, defining the datatype in terms of other datatypes.
  • Attaching a QName to the datatype.

4.1.1 The Simple Type Definition Schema Component

The Simple Type Definition schema component has the following properties:

Schema Component: Simple Type Definition
{annotations}
A sequence of Annotation components.
{name}
An xs:NCName value. Optional.
{target namespace}
An xs:anyURI value. Optional.
{final}

A subset of {restriction, extension, list, union}

{context}
Required if {name} is absent, otherwise must be absent
{base type definition}
A Type Definition component. Required.
{facets}
A set of Constraining Facet components.
{fundamental facets}
A set of Fundamental Facet components.
{variety}
One of {atomic, list, union}. Required for all Simple Type Definitions except ·anySimpleType·, in which it is absent.
{primitive type definition}
A Simple Type Definition component. With one exception, required if {variety} is atomic, otherwise must be absent. The exception is ·anyAtomicType·, whose {primitive type definition} is absent.

If not absent, must be a ·primitive· built-in definition.

{item type definition}
A Simple Type Definition component. Required if {variety} is list, otherwise must be absent.

The value of this property must be a primitive or ordinary simple type definition with {variety} = atomic, or an ordinary simple type definition with {variety} = union whose basic members are all atomic; the value must not itself be a list type (have {variety} = list) or have any basic members which are list types.

{member type definitions}
A sequence of primitive or ordinary Simple Type Definition components.

Must be present (but may be empty) if {variety} is union, otherwise must be absent.

The sequence may contain any primitive or ordinary simple type definition, but must not contain any special type definitions.

Simple type definitions are identified by their {name} and {target namespace}.  Except for anonymous Simple Type Definitions (those with no {name}), Simple Type Definitions must be uniquely identified within a schema. Within a valid schema, each Simple Type Definition uniquely determines one datatype. The ·value space·, ·lexical space·, ·lexical mapping·, etc., of a Simple Type Definition are the ·value space·, ·lexical space·, etc., of the datatype uniquely determined (or "defined") by that Simple Type Definition.

If {variety} is ·atomic· then the ·value space· of the datatype defined will be a subset of the ·value space· of {base type definition} (which is a subset of the ·value space· of {primitive type definition}). If {variety} is ·list· then the ·value space· of the datatype defined will be the set of (possibly empty) finite-length sequences of values from the ·value space· of {item type definition}. If {variety} is ·union· then the ·value space· of the datatype defined will be a subset (possibly an improper subset) of the union of the ·value spaces· of each Simple Type Definition in {member type definitions}.

If {variety} is ·atomic· then the {variety} of {base type definition} must be ·atomic·, unless the {base type definition} is anySimpleType. If {variety} is ·list· then the {variety} of {item type definition} must be either ·atomic· or ·union·, and if {item type definition} is ·union· then all its ·basic members· must be ·atomic·. If {variety} is ·union· then {member type definitions} must be a list of Simple Type Definitions.

The {facets} property determines the ·value space· and ·lexical space· of the datatype being defined by imposing constraints which are to be satisfied by all valid values and ·lexical representations·.

The {fundamental facets} property provides some basic information about the datatype being defined: its cardinality, whether an ordering is defined for it by this specification, whether it has upper and lower bounds, and whether it is numeric.

If {final} is the empty set then the type can be used in deriving other types; the explicit values restriction, list and union prevent further derivations of Simple Type Definitions by ·facet-based restriction·, ·list· and ·union· respectively; the explicit value extension prevents any derivation of Complex Type Definitions by extension.

The {context} property is only relevant for anonymous type definitions, for which its value is the component in which this type definition appears as the value of a property, e.g. {item type definition} or {base type definition}.

4.1.2 XML Representation of Simple Type Definition Schema Components

The XML representation for a Simple Type Definition schema component is a <simpleType> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: simpleType Element Information Item et al.
<simpleType
  final = (#all | List of (list | union | restriction | extension))
  id = ID
  name = NCName
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?, (restriction | list | union))
</simpleType>
<restriction
  base = QName
  id = ID
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?, (simpleType?, (minExclusive | minInclusive | maxExclusive | maxInclusive | totalDigits | fractionDigits | length | minLength | maxLength | enumeration | whiteSpace | pattern | assertion | explicitTimezone | {any with namespace: ##other})*))
</restriction>
<list
  id = ID
  itemType = QName
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?, simpleType?)
</list>
<union
  id = ID
  memberTypes = List of QName
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?, simpleType*)
</union>
Simple Type Definition Schema Component
Property
Representation
 
The actual value of the name [attribute], if present on the <simpleType> element, otherwise absent
 
The actual value of the targetNamespace [attribute] of the parent schema element information item, if present, otherwise absent.
 
The appropriate case among the following:
1 If the <restriction> alternative is chosen, then the type definition resolved to by the actual value of the base [attribute] of <restriction>, if present, otherwise the type definition corresponding to the <simpleType> among the [children] of <restriction>.
2 If the <list> or <union> alternative is chosen, then ·anySimpleType·.
 
A subset of {restriction, extension, list, union}, determined as follows. [Definition:]  Let FS be the actual value of the final [attribute], if present, otherwise the actual value of the finalDefault [attribute] of the ancestor schema element, if present, otherwise the empty string. Then the property value is the appropriate case among the following:
1 If ·FS· is the empty string, then the empty set;
2 If ·FS· is '#all', then {restriction, extension, list, union};
3 otherwise Consider ·FS· as a space-separated list, and include restriction if 'restriction' is in that list, and similarly for extension, list and union.
 
The appropriate case among the following:
1 If the name [attribute] is present, then absent
2 otherwise the appropriate case among the following:
2.1 If the parent element information item is <attribute>, then the corresponding Attribute Declaration
2.2 If the parent element information item is <element>, then the corresponding Element Declaration
2.3 If the parent element information item is <list> or <union>, then the Simple Type Definition corresponding to the grandparent <simpleType> element information item
2.4 otherwise (the parent element information item is <restriction>), the appropriate case among the following:
2.4.1 If the grandparent element information item is <simpleType>, then the Simple Type Definition corresponding to the grandparent
2.4.2 otherwise (the grandparent element information item is <simpleContent>), the Simple Type Definition which is the {content type} of the Complex Type Definition corresponding to the great-grandparent <complexType> element information item.
 
If the <list> alternative is chosen, then list, otherwise if the <union> alternative is chosen, then union, otherwise (the <restriction> alternative is chosen) the {variety} of the {base type definition}.
 
The appropriate case among the following:
1 If the <restriction> alternative is chosen, then the set of Constraining Facet components obtained by overlaying the {facets} of the {base type definition} with the set of Constraining Facet components corresponding to those [children] of <restriction> which specify facets, as defined in Schema Component Constraint: Simple Type Restriction (Facets) .
2 If the <list> alternative is chosen, then a set with one member, a whiteSpace facet with {value} = collapse and {fixed} = true.
3 otherwise the empty set
 
 
The annotation mapping of the set of elements containing the <simpleType>, and the <restriction>, the <list>, or the <union> [child], whichever is present, as defined in section XML Representation of Annotation Schema Components of [XSD 1.1 Part 1: Structures].
[Definition:]  The ancestors of a type definition are its {base type definition} and the ·ancestors· of its {base type definition}. (The ancestors of a Simple Type Definition T in the type hierarchy are themselves type definitions; they are distinct from the XML elements which may be ancestors, in the XML document hierarchy, of the <simpleType> element which declares T.)
If the {variety} is atomic, the following additional property mapping also applies:
Property
Representation
 
From among the ·ancestors· of this Simple Type Definition, that Simple Type Definition which corresponds to a ·primitive· datatype.
Example
An electronic commerce schema might define a datatype called 'SKU' (the barcode number that appears on products) from the ·built-in· datatype string by supplying a value for the ·pattern· facet.
<simpleType name='SKU'>
    <restriction base='string'>
      <pattern value='\d{3}-[A-Z]{2}'/>
    </restriction>
</simpleType>
In this case, 'SKU' is the name of the new ·user-defined· datatype, string is its ·base type· and ·pattern· is the facet.
If the {variety} is list, the following additional property mappings also apply:
Property
Representation
 
The appropriate case among the following:
1 If the {base type definition} is ·anySimpleType·, then the Simple Type Definition (a) resolved to by the actual value of the itemType [attribute] of <list>, or (b) corresponding to the <simpleType> among the [children] of <list>, whichever is present.
Note: In this case, a <list> element will invariably be present; it will invariably have either an itemType [attribute] or a <simpleType> [child], but not both.
2 otherwise (that is, the {base type definition} is not ·anySimpleType·), the {item type definition} of the {base type definition}.
Note: In this case, a <restriction> element will invariably be present.
Example
A system might want to store lists of floating point values.
<simpleType name='listOfFloat'>
  <list itemType='float'/>
</simpleType>
In this case, listOfFloat is the name of the new ·user-defined· datatype, float is its ·item type· and ·list· is the derivation method.
If the {variety} is union, the following additional property mappings also apply:
Property
Representation
 
The appropriate case among the following:
1 If the {base type definition} is ·anySimpleType·, then the sequence of (a) the Simple Type Definitions (a) resolved to by the items in the actual value of the memberTypes [attribute] of <union>, if any, and (b) those corresponding to the <simpleType>s among the [children] of <union>, if any, in order.
Note: In this case, a <union> element will invariably be present; it will invariably have either a memberTypes [attribute] or one or more <simpleType> [children], or both.
2 otherwise (that is, the {base type definition} is not ·anySimpleType·), the {member type definitions} of the {base type definition}.
Note: In this case, a <restriction> element will invariably be present.
Example
As an example, taken from a typical display oriented text markup language, one might want to express font sizes as an integer between 8 and 72, or with one of the tokens "small", "medium" or "large".  The ·union· Simple Type Definition below would accomplish that.
<xs:attribute name="size">
  <xs:simpleType>
    <xs:union>
      <xs:simpleType>
        <xs:restriction base="xs:positiveInteger">
          <xs:minInclusive value="8"/>
          <xs:maxInclusive value="72"/>
        </xs:restriction>
      </xs:simpleType>
      <xs:simpleType>
        <xs:restriction base="xs:NMTOKEN">
          <xs:enumeration value="small"/>
          <xs:enumeration value="medium"/>
          <xs:enumeration value="large"/>
        </xs:restriction>
      </xs:simpleType>
    </xs:union>
  </xs:simpleType>
</xs:attribute>
<p>
<font size='large'>A header</font>
</p>
<p>
<font size='12'>this is a test</font>
</p>

A datatype can be ·constructed· from a ·primitive· datatype or an ·ordinary· datatype by one of three means: by ·facet-based restriction·, by ·list· or by ·union·.

4.1.3 Constraints on XML Representation of Simple Type Definition

Schema Representation Constraint: itemType attribute or simpleType child
Either the itemType [attribute] or the <simpleType> [child] of the <list> element must be present, but not both.
Schema Representation Constraint: base attribute or simpleType child
Either the base [attribute] or the simpleType [child] of the <restriction> element must be present, but not both.
Schema Representation Constraint: memberTypes attribute or simpleType children
Either the memberTypes [attribute] of the <union> element must be non-empty or there must be at least one simpleType [child].

4.1.4 Simple Type Definition Validation Rules

Validation Rule: Facet Valid
A value in a ·value space· is facet-valid with respect to a ·constraining facet· component if and only if:
1 the value is facet-valid with respect to the particular ·constraining facet· as specified below.
Validation Rule: Datatype Valid
A ·literal· is datatype-valid with respect to a Simple Type Definition if and only if it is a member of the ·lexical space· of the corresponding datatype.
Note: Since every value in the ·value space· is denoted by some ·literal·, and every ·literal· in the ·lexical space· maps to some value, the requirement that the ·literal· be in the ·lexical space· entails the requirement that the value it maps to should fulfill all of the constraints imposed by the {facets} of the datatype. If the datatype is a ·list·, the Datatype Valid constraint also entails that each whitespace-delimited token in the list be datatype-valid against the ·item type· of the list. If the datatype is a ·union·, the Datatype Valid constraint entails that the ·literal· be datatype-valid against at least one of the ·member types·.
That is, the constraints on Simple Type Definitions and on datatype ·derivation· defined in this specification have as a consequence that a ·literal· L is datatype-valid with respect to a Simple Type Definition T if and only if either T corresponds to a ·special· datatype or all of the following are true:
1 If there is a pattern in {facets}, then L is pattern valid (§4.3.4.4) with respect to the pattern. If there are other ·lexical· facets in {facets}, then L is facet-valid with respect to them.
2 The appropriate case among the following is true:
2.1 If the {variety} of T is ·atomic·, then L is in the ·lexical space· of the {primitive type definition} of T, as defined in the appropriate documentation. Let V be the member of the ·value space· of the {primitive type definition} of T mapped to by L, as defined in the appropriate documentation.
Note: For ·built-in· ·primitives·, the "appropriate documentation" is the relevant section of this specification. For ·implementation-defined· ·primitives·, it is the normative specification of the ·primitive·, which will typically be included in, or referred to from, the implementation's documentation.
2.2 If the {variety} of T is ·list·, then each space-delimited substring of L is Datatype Valid with respect to the {item type definition} of T. Let V be the sequence consisting of the values identified by Datatype Valid for each of those substrings, in order.
2.3 If the {variety} of T is ·union·, then L is Datatype Valid with respect to at least one member of the {member type definitions} of T. Let B be the ·active basic member· of T for L. Let V be the value identified by Datatype Valid for L with respect to B.
3 V, as determined by the appropriate sub-clause of clause 2 above, is Facet Valid (§4.1.4) with respect to each member of the {facets} of T which is a ·value-based· (and not a ·pre-lexical· or ·lexical·) facet.
Note that whiteSpace facets and other ·pre-lexical· facets do not take part in checking Datatype Valid. In cases where this specification is used in conjunction with schema-validation of XML documents, such facets are used to normalize infoset values before the normalized results are checked for datatype validity. In the case of unions the ·pre-lexical· facets to use are those associated with B in clause 2.3 above. When more than one ·pre-lexical· facet applies, the whiteSpace facet is applied first; the order in which ·implementation-defined· facets are applied is ·implementation-defined·.

4.1.5 Constraints on Simple Type Definition Schema Components

Schema Component Constraint: Applicable Facets
The ·constraining facets· which are allowed to be members of {facets} depend on the {variety} and {primitive type definition} of the type, as follows:

If {variety} is absent, then no facets are applicable. (This is true for anySimpleType.)

If {variety} is list, then the applicable facets are assertions, length, minLength, maxLength, pattern, enumeration, and whiteSpace.

If {variety} is union, then the applicable facets are pattern, enumeration, and assertions.

If {variety} is atomic, and {primitive type definition} is absent then no facets are applicable. (This is true for anyAtomicType.)

In all other cases ({variety} is atomic and {primitive type definition} is not absent), then the applicable facets are shown in the table below.

{primitive type definition}applicable {facets}
stringlength, minLength, maxLength, pattern, enumeration, whiteSpace, assertions
booleanpattern, whiteSpace, assertions
floatpattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions
doublepattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions
decimaltotalDigits, fractionDigits, pattern, whiteSpace, enumeration, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions
durationpattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions
dateTimepattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions, explicitTimezone
timepattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions, explicitTimezone
datepattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions, explicitTimezone
gYearMonthpattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions, explicitTimezone
gYearpattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions, explicitTimezone
gMonthDaypattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions, explicitTimezone
gDaypattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions, explicitTimezone
gMonthpattern, enumeration, whiteSpace, maxInclusive, maxExclusive, minInclusive, minExclusive, assertions, explicitTimezone
hexBinarylength, minLength, maxLength, pattern, enumeration, whiteSpace, assertions
base64Binarylength, minLength, maxLength, pattern, enumeration, whiteSpace, assertions
anyURIlength, minLength, maxLength, pattern, enumeration, whiteSpace, assertions
QNamelength, minLength, maxLength, pattern, enumeration, whiteSpace, assertions
NOTATIONlength, minLength, maxLength, pattern, enumeration, whiteSpace, assertions
Note: For any ·implementation-defined· primitive types, it is ·implementation-defined· which constraining facets are applicable to them.
Similarly, for any ·implementation-defined· constraining facets, it is ·implementation-defined· which ·primitives· they apply to.

4.1.6 Built-in Simple Type Definitions

The Simple Type Definition of anySimpleType is present in every schema.  It has the following properties:

The definition of anySimpleType is the root of the Simple Type Definition hierarchy; as such it mediates between the other simple type definitions, which all eventually trace back to it via their {base type definition} properties, and the definition of anyType, which is its {base type definition}.

The Simple Type Definition of anyAtomicType is present in every schema.  It has the following properties:

Simple type definitions for all the built-in primitive datatypes, namely string, boolean, float, double, decimal, dateTime, duration, time, date, gMonth, gMonthDay, gDay, gYear, gYearMonth, hexBinary, base64Binary, anyURI are present by definition in every schema.  All have a very similar structure, with only the {name}, the {primitive type definition} (which is self-referential), the {fundamental facets}, and in one case the {facets} varying from one to the next:

Property
Value
[as appropriate]
'http://www.w3.org/2001/XMLSchema'
The empty set
atomic
{a whiteSpace facet with {value} = collapse and {fixed} = true in all cases except string, which has {value} = preserve and {fixed} = false}
[as appropriate]
absent
The empty sequence
·Implementation-defined· ·primitives· must have a Simple Type Definition with the values shown above, with the following exceptions.
  1. The {facets} property must contain a whiteSpace facet, the value of which is ·implementation-defined·. It may contain other facets, whether defined in this specification or ·implementation-defined·.
  2. The value of {annotations} may be empty, but need not be.
Note: It is a consequence of the rule just given that each ·implementation-defined· ·primitive· will have an expanded name by which it can be referred to.
Note: ·Implementation-defined· datatypes will normally have a value other than 'http://www.w3.org/2001/XMLSchema' for the {target namespace} property. That namespace is controlled by the W3C and datatypes will be added to it only by W3C or its designees.

Similarly, Simple Type Definitions for all the built-in ·ordinary· datatypes are present by definition in every schema, with properties as specified in Other Built-in Datatypes (§3.4) and as represented in XML in Illustrative XML representations for the built-in ordinary type definitions (§C.2).

Property
Value
[as appropriate]
'http://www.w3.org/2001/XMLSchema'
[as specified in the appropriate sub-section of Other Built-in Datatypes (§3.4)]
The empty set
[atomic or list, as specified in the appropriate sub-section of Other Built-in Datatypes (§3.4)]
[as specified in the appropriate sub-section of Other Built-in Datatypes (§3.4)]
[as specified in the appropriate sub-section of Other Built-in Datatypes (§3.4)]
absent
if {variety} is atomic, then absent, otherwise as specified in the appropriate sub-section of Other Built-in Datatypes (§3.4)]
As shown in the XML representations of the ordinary built-in datatypes in Illustrative XML representations for the built-in ordinary type definitions (§C.2)

previous sub-section next sub-section4.2 Fundamental Facets

        4.2.1 ordered
            4.2.1.1 The ordered Schema Component
        4.2.2 bounded
            4.2.2.1 The bounded Schema Component
        4.2.3 cardinality
            4.2.3.1 The cardinality Schema Component
        4.2.4 numeric
            4.2.4.1 The numeric Schema Component

[Definition:]   Each fundamental facet is a schema component that provides a limited piece of information about some aspect of each datatype.  All ·fundamental facet· components are defined in this section.  For example, cardinality is a ·fundamental facet·.  Most ·fundamental facets· are given a value fixed with each primitive datatype's definition, and this value is not changed by subsequent ·derivations· (even when it would perhaps be reasonable to expect an application to give a more accurate value based on the constraining facets used to define the ·derivation·).  The cardinality and bounded facets are exceptions to this rule; their values may change as a result of certain ·derivations·.

Note: Schema components are identified by kind.  "Fundamental" is not a kind of component.  Each kind of ·fundamental facet· ("ordered", "bounded", etc.) is a separate kind of schema component.

A ·fundamental facet· can occur only in the {fundamental facets} of a Simple Type Definition, and this is the only place where ·fundamental facet· components occur.    Each kind of ·fundamental facet· component occurs (once) in each Simple Type Definition's {fundamental facets} set.

Note: The value of any ·fundamental facet· component can always be calculated from other properties of its ·owner·.  Fundamental facets are not required for schema processing, but some applications use them.

4.2.1 ordered

For some datatypes, this document specifies an order relation for their value spaces (see Order (§2.2.3)); the ordered facet reflects this. It takes the values total, partial, and false, with the meanings described below. For the ·primitive· datatypes, the value of the ordered facet is specified in Fundamental Facets (§F.1). For ·ordinary· datatypes, the value is inherited without change from the ·base type·. For a ·list·, the value is always false; for a ·union·, the value is computed as described below.

A false value means no order is prescribed; a total value assures that the prescribed order is a total order; a partial value means that the prescribed order is a partial order, but not (for the primitive type in question) a total order.

Note: The value false in the ordered facet does not mean no partial or total ordering exists for the value space, only that none is specified by this document for use in checking upper and lower bounds. Mathematically, any set of values possesses at least one trivial partial ordering, in which every value pair that is not equal is incomparable.
Note: When new datatypes are derived from datatypes with partial orders, the constraints imposed can sometimes result in a value space for which the ordering is total, or trivial. The value of the ordered facet is not, however, changed to reflect this. The value partial should therefore be interpreted with appropriate caution.

[Definition:]  A ·value space·, and hence a datatype, is said to be ordered if some members of the ·value space· are drawn from a ·primitive· datatype for which the table in Fundamental Facets (§F.1) specifies the value total or partial for the ordered facet.

Note: Some of the "real-world" datatypes which are the basis for those defined herein are ordered in some applications, even though no order is prescribed for schema-processing purposes.  For example, boolean is sometimes ordered, and string and ·list· datatypes ·constructed· from ordered ·atomic· datatypes are sometimes given "lexical" orderings.  They are not ordered for schema-processing purposes.
4.2.1.1 The ordered Schema Component
Schema Component: ordered, a kind of Fundamental Facet
{value}
One of {false, partial, total}. Required.
{value} depends on the ·owner's· {variety}, {facets}, and {member type definitions}. The appropriate case among the following must be true:
1 If the ·owner's· {variety} is atomic, then the appropriate case among the following must be true:
1.1 If the ·owner· is ·primitive·, then {value} is as specified in the table in Fundamental Facets (§F.1).
2 If the ·owner's· {variety} is list, then {value} is false.
3 otherwise the ·owner's· {variety} is union; the appropriate case among the following must be true:
3.1 If every ·basic member· of the ·owner· has {variety} atomic and has the same {primitive type definition}, then {value} is the same as the ordered component's {value} in that primitive type definition's {fundamental facets}.
3.2 If each member of the ·owner's· {member type definitions} has an ordered component in its {fundamental facets} whose {value} is false, then {value} is false.
3.3 otherwise {value} is partial.

4.2.2 bounded

Some ordered datatypes have the property that there is one value greater than or equal to every other value, and another that is less than or equal to every other value.  (In the case of ·ordinary· datatypes, these two values are not necessarily in the value space of the derived datatype, but they will always be in the value space of the primitive datatype from which they have been derived.) The bounded facet value is boolean and is generally true for such bounded datatypes.  However, it will remain false when the mechanism for imposing such a bound is difficult to detect, as, for example, when the boundedness occurs because of derivation using a pattern component.

4.2.2.1 The bounded Schema Component
Schema Component: bounded, a kind of Fundamental Facet
{value}
An xs:boolean value. Required.

{value} depends on the ·owner's· {variety}, {facets} and {member type definitions}.

When the ·owner· is ·primitive·, {value} is as specified in the table in Fundamental Facets (§F.1).  Otherwise, when the ·owner's· {variety} is atomic, if one of minInclusive or minExclusive and one of maxInclusive or maxExclusive are members of the ·owner's· {facets} set, then {value} is true; otherwise {value} is false.

When the ·owner's· {variety} is list, {value} is false.

When the ·owner's· {variety} is union, if {value} is true for every member of the ·owner's· {member type definitions} set and all of the ·owner's· ·basic members· have the same {primitive type definition}, then {value} is true; otherwise {value} is false.

4.2.3 cardinality

Every value space has a specific number of members.  This number can be characterized as finite or infinite.  (Currently there are no datatypes with infinite value spaces larger than countable.)  The cardinality facet value is either finite or countably infinite and is generally finite for datatypes with finite value spaces.  However, it will remain countably infinite when the mechanism for causing finiteness is difficult to detect, as, for example, when finiteness occurs because of a derivation using a pattern component.

4.2.3.1 The cardinality Schema Component
Schema Component: cardinality, a kind of Fundamental Facet
{value}
One of {finite, countably infinite}. Required.

{value} depends on the ·owner's· {variety}, {facets}, and {member type definitions}.

When the ·owner· is ·primitive·, {value} is as specified in the table in Fundamental Facets (§F.1).  Otherwise, when the ·owner's· {variety} is atomic, {value} is countably infinite unless any of the following conditions are true, in which case {value} is finite:
  1. at least one of length, maxLength, or totalDigits is a member of the ·owner's· {facets} set,
  2. all of the following are true:
    1. one of minInclusive or minExclusive is a member of the ·owner's· {facets} set
    2. one of maxInclusive or maxExclusive is a member of the ·owner's· {facets} set
    3. either of the following are true:
      1. fractionDigits is a member of the ·owner's· {facets} set

When the ·owner's· {variety} is list, if length or both minLength and maxLength are members of the ·owner's· {facets} set and the ·owner's· {item type definition}'s cardinality {value} is finite then {value} is finite; otherwise {value} is countably infinite.

When the ·owner's· {variety} is union, if cardinality's {value} is finite for every member of the ·owner's· {member type definitions} set then {value} is finite, otherwise {value} is countably infinite.

4.2.4 numeric

Some value spaces are made up of things that are conceptually numeric, others are not. The numeric facet value indicates which are considered numeric.

4.2.4.1 The numeric Schema Component
Schema Component: numeric, a kind of Fundamental Facet
{value}
An xs:boolean value. Required.

{value} depends on the ·owner's· {variety}, {facets}, {base type definition} and {member type definitions}.

When the ·owner· is ·primitive·, {value} is as specified in the table in Fundamental Facets (§F.1).  Otherwise, when the ·owner's· {variety} is atomic, {value} is inherited from the ·owner's· {base type definition}'s numeric{value}.

When the ·owner's· {variety} is list, {value} is false.

When the ·owner's· {variety} is union, if numeric's {value} is true for every member of the ·owner's· {member type definitions} set then {value} is true, otherwise {value} is false.

previous sub-section 4.3 Constraining Facets

        4.3.1 length
            4.3.1.1 The length Schema Component
            4.3.1.2 XML Representation of length Schema Components
            4.3.1.3 length Validation Rules
            4.3.1.4 Constraints on length Schema Components
        4.3.2 minLength
            4.3.2.1 The minLength Schema Component
            4.3.2.2 XML Representation of minLength Schema Component
            4.3.2.3 minLength Validation Rules
            4.3.2.4 Constraints on minLength Schema Components
        4.3.3 maxLength
            4.3.3.1 The maxLength Schema Component
            4.3.3.2 XML Representation of maxLength Schema Components
            4.3.3.3 maxLength Validation Rules
            4.3.3.4 Constraints on maxLength Schema Components
        4.3.4 pattern
            4.3.4.1 The pattern Schema Component
            4.3.4.2 XML Representation of pattern Schema Components
            4.3.4.3 Constraints on XML Representation of pattern
            4.3.4.4 pattern Validation Rules
            4.3.4.5 Constraints on pattern Schema Components
        4.3.5 enumeration
            4.3.5.1 The enumeration Schema Component
            4.3.5.2 XML Representation of enumeration Schema Components
            4.3.5.3 Constraints on XML Representation of enumeration
            4.3.5.4 enumeration Validation Rules
            4.3.5.5 Constraints on enumeration Schema Components
        4.3.6 whiteSpace
            4.3.6.1 The whiteSpace Schema Component
            4.3.6.2 XML Representation of whiteSpace Schema Components
            4.3.6.3 whiteSpace Validation Rules
            4.3.6.4 Constraints on whiteSpace Schema Components
        4.3.7 maxInclusive
            4.3.7.1 The maxInclusive Schema Component
            4.3.7.2 XML Representation of maxInclusive Schema Components
            4.3.7.3 maxInclusive Validation Rules
            4.3.7.4 Constraints on maxInclusive Schema Components
        4.3.8 maxExclusive
            4.3.8.1 The maxExclusive Schema Component
            4.3.8.2 XML Representation of maxExclusive Schema Components
            4.3.8.3 maxExclusive Validation Rules
            4.3.8.4 Constraints on maxExclusive Schema Components
        4.3.9 minExclusive
            4.3.9.1 The minExclusive Schema Component
            4.3.9.2 XML Representation of minExclusive Schema Components
            4.3.9.3 minExclusive Validation Rules
            4.3.9.4 Constraints on minExclusive Schema Components
        4.3.10 minInclusive
            4.3.10.1 The minInclusive Schema Component
            4.3.10.2 XML Representation of minInclusive Schema Components
            4.3.10.3 minInclusive Validation Rules
            4.3.10.4 Constraints on minInclusive Schema Components
        4.3.11 totalDigits
            4.3.11.1 The totalDigits Schema Component
            4.3.11.2 XML Representation of totalDigits Schema Components
            4.3.11.3 totalDigits Validation Rules
            4.3.11.4 Constraints on totalDigits Schema Components
        4.3.12 fractionDigits
            4.3.12.1 The fractionDigits Schema Component
            4.3.12.2 XML Representation of fractionDigits Schema Components
            4.3.12.3 fractionDigits Validation Rules
            4.3.12.4 Constraints on fractionDigits Schema Components
        4.3.13 Assertions
            4.3.13.1 The assertions Schema Component
            4.3.13.2 XML Representation of assertions Schema Components
            4.3.13.3 Assertions Validation Rules
            4.3.13.4 Constraints on assertions Schema Components
        4.3.14 explicitTimezone
            4.3.14.1 The explicitTimezone Schema Component
            4.3.14.2 XML Representation of explicitTimezone Schema Components
            4.3.14.3 explicitTimezone Validation Rules
            4.3.14.4 Constraints on explicitTimezone Schema Components

[Definition:]  Constraining facets are schema components whose values may be set or changed during ·derivation· (subject to facet-specific controls) to control various aspects of the derived datatype.  All ·constraining facet· components defined by this specification are defined in this section.  For example, whiteSpace is a ·constraining facet··Constraining Facets· are given a value as part of the ·derivation· when an ·ordinary· datatype is defined by ·restricting· a ·primitive· or ·ordinary· datatype; a few ·constraining facets· have default values that are also provided for ·primitive· datatypes.

Note: Schema components are identified by kind.  "Constraining" is not a kind of component.  Each kind of ·constraining facet· ("whiteSpace", "length", etc.) is a separate kind of schema component.
This specification distinguishes three kinds of constraining facets:

Conforming processors must support all the facets defined in this section. It is ·implementation-defined· whether a processor supports other constraining facets. [Definition:]  An ·constraining facet· which is not supported by the processor in use is unknown.

Note: A reference to an ·unknown· facet might be a reference to an ·implementation-defined· facet supported by some other processor, or might be the result of a typographic error, or might have some other explanation.

The descriptions of individual facets given below include both constraints on Simple Type Definition components and rules for checking the datatype validity of a given literal against a given datatype. The validation rules typically depend upon having a full knowledge of the datatype; full knowledge of the datatype, in turn, depends on having a fully instantiated Simple Type Definition. A full instantiation of the Simple Type Definition, and the checking of the component constraints, require knowledge of the ·base type·. It follows that if a datatype's ·base type· is ·unknown·, the Simple Type Definition defining the datatype will be incompletely instantiated, and the datatype itself will be ·unknown·. Similarly, any datatype defined using an ·unknown· ·constraining facet· will be ·unknown·. It is not possible to perform datatype validation as defined here using ·unknown· datatypes.

Note: The preceding paragraph does not forbid implementations from attempting to make use of such partial information as they have about ·unknown· datatypes. But the exploitation of such partial knowledge is not datatype validity checking as defined here and is to be distinguished from it in the implementation's documentation and interface.

4.3.1 length

[Definition:]   length is the number of units of length, where units of length varies depending on the type that is being ·derived· from. The value of length must be a nonNegativeInteger.

For string and datatypes ·derived· from string, length is measured in units of characters as defined in [XML]. For anyURI, length is measured in units of characters (as for string). For hexBinary and base64Binary and datatypes ·derived· from them, length is measured in octets (8 bits) of binary data. For datatypes ·constructed· by ·list·, length is measured in number of list items.

Note: For string and datatypes ·derived· from string, length will not always coincide with "string length" as perceived by some users or with the number of storage units in some digital representation.  Therefore, care should be taken when specifying a value for length and in attempting to infer storage requirements from a given value for length.

·length· provides for:

Example
The following is the definition of a ·user-defined· datatype to represent product codes which must be exactly 8 characters in length.  By fixing the value of the length facet we ensure that types derived from productCode can change or set the values of other facets, such as pattern, but cannot change the length.
<simpleType name='productCode'>
   <restriction base='string'>
     <length value='8' fixed='true'/>
   </restriction>
</simpleType>
4.3.1.1 The length Schema Component
Schema Component: length, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
An xs:nonNegativeInteger value. Required.
{fixed}
An xs:boolean value. Required.

If {fixed} is true, then types for which the current type is the {base type definition} cannot specify a value for length other than {value}.

Note: The {fixed} property is defined for parallelism with other facets and for compatibility with version 1.0 of this specification. But it is a consequence of length valid restriction (§4.3.1.4) that the value of the length facet cannot be changed, regardless of whether {fixed} is true or false.
4.3.1.2 XML Representation of length Schema Components

The XML representation for a length schema component is a <length> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: length Element Information Item
<length
  fixed = boolean : false
  id = ID
  value = nonNegativeInteger
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</length>
length Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.1.3 length Validation Rules
Validation Rule: Length Valid
A value in a ·value space· is facet-valid with respect to ·length· if and only if:
1 if the {variety} is ·atomic· then
1.1 if {primitive type definition} is string or anyURI, then the length of the value, as measured in characters must be equal to {value};
1.2 if {primitive type definition} is hexBinary or base64Binary, then the length of the value, as measured in octets of the binary data, must be equal to {value};
1.3 if {primitive type definition} is QName or NOTATION, then any {value} is facet-valid.
2 if the {variety} is ·list·, then the length of the value, as measured in list items, must be equal to {value}

The use of ·length· on QName, NOTATION, and datatypes ·derived· from them is deprecated.  Future versions of this specification may remove this facet for these datatypes.

4.3.1.4 Constraints on length Schema Components
Schema Component Constraint: length and minLength or maxLength
If length is a member of {facets} then
1 It is an error for minLength to be a member of {facets} unless
1.1 the {value} of minLength <= the {value} of length and
1.2 there is some type definition from which this one is derived by one or more ·restriction· steps in which minLength has the same {value} and length is not specified.
2 It is an error for maxLength to be a member of {facets} unless
2.1 the {value} of length <= the {value} of maxLength and
2.2 there is some type definition from which this one is derived by one or more restriction steps in which maxLength has the same {value} and length is not specified.
Schema Component Constraint: length valid restriction
It is an ·error· if length is among the members of {facets} of {base type definition} and {value} is not equal to the {value} of the parent length.

4.3.2 minLength

[Definition:]   minLength is the minimum number of units of length, where units of length varies depending on the type that is being ·derived· from. The value of minLength  must be a nonNegativeInteger.

For string and datatypes ·derived· from string, minLength is measured in units of characters as defined in [XML]. For hexBinary and base64Binary and datatypes ·derived· from them, minLength is measured in octets (8 bits) of binary data. For datatypes ·constructed· by ·list·, minLength is measured in number of list items.

Note: For string and datatypes ·derived· from string, minLength will not always coincide with "string length" as perceived by some users or with the number of storage units in some digital representation. Therefore, care should be taken when specifying a value for minLength and in attempting to infer storage requirements from a given value for minLength.

·minLength· provides for:

Example
The following is the definition of a ·user-defined· datatype which requires strings to have at least one character (i.e., the empty string is not in the ·value space· of this datatype).
<simpleType name='non-empty-string'>
  <restriction base='string'>
    <minLength value='1'/>
  </restriction>
</simpleType>
4.3.2.1 The minLength Schema Component
Schema Component: minLength, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
An xs:nonNegativeInteger value. Required.
{fixed}
An xs:boolean value. Required.

If {fixed} is true, then types for which the current type is the {base type definition} cannot specify a value for minLength other than {value}.

4.3.2.2 XML Representation of minLength Schema Component

The XML representation for a minLength schema component is a <minLength> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: minLength Element Information Item
<minLength
  fixed = boolean : false
  id = ID
  value = nonNegativeInteger
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</minLength>
minLength Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.2.3 minLength Validation Rules
Validation Rule: minLength Valid
A value in a ·value space· is facet-valid with respect to ·minLength·, determined as follows:
1 if the {variety} is ·atomic· then
1.1 if {primitive type definition} is string or anyURI, then the length of the value, as measured in characters must be greater than or equal to {value};
1.2 if {primitive type definition} is hexBinary or base64Binary, then the length of the value, as measured in octets of the binary data, must be greater than or equal to {value};
1.3 if {primitive type definition} is QName or NOTATION, then any {value} is facet-valid.
2 if the {variety} is ·list·, then the length of the value, as measured in list items, must be greater than or equal to {value}

The use of ·minLength· on QName, NOTATION, and datatypes ·derived· from them is deprecated.  Future versions of this specification may remove this facet for these datatypes.

4.3.2.4 Constraints on minLength Schema Components
Schema Component Constraint: minLength <= maxLength
If both minLength and maxLength are members of {facets}, then the {value} of minLength  must be less than or equal to the {value} of maxLength.
Schema Component Constraint: minLength valid restriction
It is an ·error· if minLength is among the members of {facets} of {base type definition} and {value} is less than the {value} of the parent minLength.

4.3.3 maxLength

[Definition:]   maxLength is the maximum number of units of length, where units of length varies depending on the type that is being ·derived· from. The value of maxLength  must be a nonNegativeInteger.

For string and datatypes ·derived· from string, maxLength is measured in units of characters as defined in [XML]. For hexBinary and base64Binary and datatypes ·derived· from them, maxLength is measured in octets (8 bits) of binary data. For datatypes ·constructed· by ·list·, maxLength is measured in number of list items.

Note: For string and datatypes ·derived· from string, maxLength will not always coincide with "string length" as perceived by some users or with the number of storage units in some digital representation. Therefore, care should be taken when specifying a value for maxLength and in attempting to infer storage requirements from a given value for maxLength.

·maxLength· provides for:

Example
The following is the definition of a ·user-defined· datatype which might be used to accept form input with an upper limit to the number of characters that are acceptable.
<simpleType name='form-input'>
  <restriction base='string'>
    <maxLength value='50'/>
  </restriction>
</simpleType>
4.3.3.1 The maxLength Schema Component
Schema Component: maxLength, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
An xs:nonNegativeInteger value. Required.
{fixed}
An xs:boolean value. Required.

If {fixed} is true, then types for which the current type is the {base type definition} cannot specify a value for maxLength other than {value}.

4.3.3.2 XML Representation of maxLength Schema Components

The XML representation for a maxLength schema component is a <maxLength> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: maxLength Element Information Item
<maxLength
  fixed = boolean : false
  id = ID
  value = nonNegativeInteger
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</maxLength>
maxLength Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.3.3 maxLength Validation Rules
Validation Rule: maxLength Valid
A value in a ·value space· is facet-valid with respect to ·maxLength·, determined as follows:
1 if the {variety} is ·atomic· then
1.1 if {primitive type definition} is string or anyURI, then the length of the value, as measured in characters must be less than or equal to {value};
1.2 if {primitive type definition} is hexBinary or base64Binary, then the length of the value, as measured in octets of the binary data, must be less than or equal to {value};
1.3 if {primitive type definition} is QName or NOTATION, then any {value} is facet-valid.
2 if the {variety} is ·list·, then the length of the value, as measured in list items, must be less than or equal to {value}

The use of ·maxLength· on QName, NOTATION, and datatypes ·derived· from them is deprecated.  Future versions of this specification may remove this facet for these datatypes.

4.3.3.4 Constraints on maxLength Schema Components
Schema Component Constraint: maxLength valid restriction
It is an ·error· if maxLength is among the members of {facets} of {base type definition} and {value} is greater than the {value} of the parent maxLength.

4.3.4 pattern

[Definition:]   pattern is a constraint on the ·value space· of a datatype which is achieved by constraining the ·lexical space· to ·literals· which match each member of a set of ·regular expressions·.  The value of pattern  must be a set of ·regular expressions·.

Note: An XML <restriction> containing more than one <pattern> element gives rise to a single ·regular expression· in the set; this ·regular expression· is an "or" of the ·regular expressions· that are the content of the <pattern> elements.

·pattern· provides for:

Example
The following is the definition of a ·user-defined· datatype which is a better representation of postal codes in the United States, by limiting strings to those which are matched by a specific ·regular expression·.
<simpleType name='better-us-zipcode'>
  <restriction base='string'>
    <pattern value='[0-9]{5}(-[0-9]{4})?'/>
  </restriction>
</simpleType>
4.3.4.1 The pattern Schema Component
Schema Component: pattern, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}

A non-empty set of ·regular expressions·.

4.3.4.2 XML Representation of pattern Schema Components

The XML representation for a pattern schema component is one or more <pattern> element information items. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: pattern Element Information Item
<pattern
  id = ID
  value = string
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</pattern>
pattern Schema Component
Property
Representation
 
[Definition:]  Let R be a regular expression given by the appropriate case among the following:
1 If there is only one <pattern> among the [children] of a <restriction>, then the actual value of its value [attribute]
2 otherwise the concatenation of the actual values of all the <pattern> [children]'s value [attributes], in order, separated by '|', so forming a single regular expression with multiple ·branches·.
The value is then given by the appropriate case among the following:
1 If the {base type definition} of the ·owner· has a pattern facet among its {facets}, then the union of that pattern facet's {value} and {·R·}
2 otherwise just {·R·}
 
The annotation mapping of the set containing all of the <pattern> elements among the [children] of the <restriction> element information item, as defined in section XML Representation of Annotation Schema Components of [XSD 1.1 Part 1: Structures].
Note: The {value} property will only have more than one member when ·facet-based restriction· involves a pattern facet at more than one step in a type derivation. During validation, lexical forms will be checked against every member of the resulting {value}, effectively creating a conjunction of patterns.
In summary, ·pattern· facets specified on the same step in a type derivation are ORed together, while ·pattern· facets specified on different steps of a type derivation are ANDed together.
Thus, to impose two ·pattern· constraints simultaneously, schema authors may either write a single ·pattern· which expresses the intersection of the two ·pattern·s they wish to impose, or define each ·pattern· on a separate type derivation step.
4.3.4.3 Constraints on XML Representation of pattern
Schema Representation Constraint: Pattern value
4.3.4.4 pattern Validation Rules
Validation Rule: pattern valid
A ·literal· in a ·lexical space· is pattern-valid (or: facet-valid with respect to ·pattern·) if and only if for each ·regular expression· in its {value}, the ·literal· is among the set of character sequences denoted by the ·regular expression·.
Note: As noted in Datatype (§2.1), certain uses of the ·pattern· facet may eliminate from the lexical space the canonical forms of some values in the value space; this can be inconvenient for applications which write out the canonical form of a value and rely on being able to read it in again as a legal lexical form. This specification provides no recourse in such situations; applications are free to deal with it as they see fit. Caution is advised.
4.3.4.5 Constraints on pattern Schema Components
Schema Component Constraint: Valid restriction of pattern
It is an ·error· if there is any member of the {value} of the pattern facet on the {base type definition} which is not also a member of the {value}.
Note: For components constructed from XML representations in schema documents, the satisfaction of this constraint is a consequence of the XML mapping rules: any pattern imposed by a simple type definition S will always also be imposed by any type derived from S by ·facet-based restriction·. This constraint ensures that components constructed by other means (so-called "born-binary" components) similarly preserve pattern facets across ·facet-based restriction·.

4.3.5 enumeration

[Definition:]   enumeration constrains the ·value space· to a specified set of values.

enumeration does not impose an order relation on the ·value space· it creates; the value of the ·ordered· property of the ·derived· datatype remains that of the datatype from which it is ·derived·.

·enumeration· provides for:

Example
The following example is a Simple Type Definition for a ·user-defined· datatype which limits the values of dates to the three US holidays enumerated. This Simple Type Definition would appear in a schema authored by an "end-user" and shows how to define a datatype by enumerating the values in its ·value space·.  The enumerated values must be type-valid ·literals· for the ·base type·.
<simpleType name='holidays'>
    <annotation>
        <documentation>some US holidays</documentation>
    </annotation>
    <restriction base='gMonthDay'>
      <enumeration value='--01-01'>
        <annotation>
            <documentation>New Year's day</documentation>
        </annotation>
      </enumeration>
      <enumeration value='--07-04'>
        <annotation>
            <documentation>4th of July</documentation>
        </annotation>
      </enumeration>
      <enumeration value='--12-25'>
        <annotation>
            <documentation>Christmas</documentation>
        </annotation>
      </enumeration>
    </restriction>
</simpleType>
4.3.5.1 The enumeration Schema Component
Schema Component: enumeration, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}

A set of values from the ·value space· of the {base type definition}.

4.3.5.2 XML Representation of enumeration Schema Components

The XML representation for an enumeration schema component is one or more <enumeration> element information items. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: enumeration Element Information Item
<enumeration
  id = ID
  value = anySimpleType
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</enumeration>
enumeration Schema Component
Property
Representation
 
The appropriate case among the following:
1 If there is only one <enumeration> among the [children] of a <restriction>, then a set with one member, the actual value of its value [attribute], interpreted as an instance of the {base type definition}.
2 otherwise a set of the actual values of all the <enumeration> [children]'s value [attributes], interpreted as instances of the {base type definition}.
Note: The value [attribute] is declared as having type ·anySimpleType·, but the {value} property of the enumeration facet must be a member of the {base type definition}. So in mapping from the XML representation to the enumeration component, the actual value is identified by using the ·lexical mapping· of the {base type definition}.
 
A (possibly empty) sequence of Annotation components, one for each <annotation> among the [children] of the <enumeration>s among the [children] of a <restriction>, in order.
4.3.5.3 Constraints on XML Representation of enumeration
Schema Representation Constraint: Enumeration value
The normalized value of the value [attribute] must be Datatype Valid (§4.1.4) with respect to the {base type definition} of the Simple Type Definition corresponding to the nearest <simpleType> ancestor element.
4.3.5.4 enumeration Validation Rules
Validation Rule: enumeration valid
A value in a ·value space· is facet-valid with respect to ·enumeration· if and only if the value is equal or identical to one of the values specified in {value}.
Note: As specified normatively elsewhere, for purposes of checking enumerations, no distinction is made between an atomic value V and a list of length one containing V as its only item.
In this question, the behavior of this specification is thus the same as the behavior specified by [XQuery 1.0 and XPath 2.0 Functions and Operators] and related specifications.
4.3.5.5 Constraints on enumeration Schema Components
Schema Component Constraint: enumeration valid restriction
It is an ·error· if any member of {value} is not in the ·value space· of {base type definition}.

4.3.6 whiteSpace

[Definition:]   whiteSpace constrains the ·value space· of types ·derived· from string such that the various behaviors specified in Attribute Value Normalization in [XML] are realized.  The value of whiteSpace must be one of {preserve, replace, collapse}.

preserve
No normalization is done, the value is not changed (this is the behavior required by [XML] for element content)
replace
All occurrences of #x9 (tab), #xA (line feed) and #xD (carriage return) are replaced with #x20 (space)
collapse
After the processing implied by replace, contiguous sequences of #x20's are collapsed to a single #x20, and any #x20 at the start or end of the string is then removed.
Note: The notation #xA used here (and elsewhere in this specification) represents the Universal Character Set (UCS) code point hexadecimal A (line feed), which is denoted by U+000A.  This notation is to be distinguished from &#xA;, which is the XML character reference to that same UCS code point.

whiteSpace is applicable to all ·atomic· and ·list· datatypes.  For all ·atomic· datatypes other than string (and types ·derived· by ·facet-based restriction· from it) the value of whiteSpace is collapse and cannot be changed by a schema author; for string the value of whiteSpace is preserve; for any type ·derived· by ·facet-based restriction· from string the value of whiteSpace can be any of the three legal values (as long as the value is at least as restrictive as the value of the ·base type·; see Constraints on whiteSpace Schema Components (§4.3.6.4)).  For all datatypes ·constructed· by ·list· the value of whiteSpace is collapse and cannot be changed by a schema author.  For all datatypes ·constructed· by ·union·  whiteSpace does not apply directly; however, the normalization behavior of ·union· types is controlled by the value of whiteSpace on that one of the ·basic members· against which the ·union· is successfully validated.

Note: For more information on whiteSpace, see the discussion on white space normalization in Schema Component Details in [XSD 1.1 Part 1: Structures].

·whiteSpace· provides for:

  • Constraining a ·value space· according to the white space normalization rules.
Example
The following example is the Simple Type Definition for the ·built-in· token datatype.
<simpleType name='token'>
    <restriction base='normalizedString'>
      <whiteSpace value='collapse'/>
    </restriction>
</simpleType>
Note: The values "replace" and "collapse" may appear to provide a convenient way to "unwrap" text (i.e. undo the effects of pretty-printing and word-wrapping). In some cases, especially highly constrained data consisting of lists of artificial tokens such as part numbers or other identifiers, this appearance is correct. For natural-language data, however, the whitespace processing prescribed for these values is not only unreliable but will systematically remove the information needed to perform unwrapping correctly. For Asian scripts, for example, a correct unwrapping process will replace line boundaries not with blanks but with zero-width separators or nothing. In consequence, it is normally unwise to use these values for natural-language data, or for any data other than lists of highly constrained tokens.
4.3.6.1 The whiteSpace Schema Component
Schema Component: whiteSpace, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
One of {preserve, replace, collapse}. Required.
{fixed}
An xs:boolean value. Required.

If {fixed} is true, then types for which the current type is the {base type definition} cannot specify a value for whiteSpace other than {value}.

4.3.6.2 XML Representation of whiteSpace Schema Components

The XML representation for a whiteSpace schema component is a <whiteSpace> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: whiteSpace Element Information Item
<whiteSpace
  fixed = boolean : false
  id = ID
  value = (collapse | preserve | replace)
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</whiteSpace>
whiteSpace Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.6.3 whiteSpace Validation Rules
Note: There are no ·Validation Rule·s associated with ·whiteSpace·. For more information, see the discussion on white space normalization in Schema Component Details in [XSD 1.1 Part 1: Structures], in particular the section 3.1.4 White Space Normalization during Validation.
4.3.6.4 Constraints on whiteSpace Schema Components
Schema Component Constraint: whiteSpace valid restriction
It is an ·error· if whiteSpace is among the members of {facets} of {base type definition} and any of the following conditions is true:
1 {value} is replace or preserve and the {value} of the parent whiteSpace is collapse
2 {value} is preserve and the {value} of the parent whiteSpace is replace
Note: In order of increasing restrictiveness, the legal values for the whiteSpace facet are preserve, collapse, and replace. The more restrictive keywords are more restrictive not in the sense of accepting progressively fewer instance documents but in the sense that each corresponds to a progressively smaller, more tightly restricted value space.

4.3.7 maxInclusive

[Definition:]   maxInclusive is the inclusive upper bound of the ·value space· for a datatype with the ·ordered· property.  The value of maxInclusive must be equal to some value in the ·value space· of the ·base type·.

·maxInclusive· provides for:

  • Constraining a ·value space· to values with a specific inclusive upper bound.
Example
The following is the definition of a ·user-defined· datatype which limits values to integers less than or equal to 100, using ·maxInclusive·.
<simpleType name='one-hundred-or-less'>
  <restriction base='integer'>
    <maxInclusive value='100'/>
  </restriction>
</simpleType>
4.3.7.1 The maxInclusive Schema Component
Schema Component: maxInclusive, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
Required.

A value from the ·value space· of the {base type definition}.

{fixed}
An xs:boolean value. Required.

If {fixed} is true, then types for which the current type is the {base type definition} cannot specify a value for maxInclusive other than {value}.

4.3.7.2 XML Representation of maxInclusive Schema Components

The XML representation for a maxInclusive schema component is a <maxInclusive> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: maxInclusive Element Information Item
<maxInclusive
  fixed = boolean : false
  id = ID
  value = anySimpleType
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</maxInclusive>
{value} must be equal to some value in the ·value space· of {base type definition}.
maxInclusive Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.7.3 maxInclusive Validation Rules
Validation Rule: maxInclusive Valid
A value in an ·ordered· ·value space· is facet-valid with respect to ·maxInclusive· if and only if the value is less than or equal to {value}, according to the datatype's order relation.
4.3.7.4 Constraints on maxInclusive Schema Components
Schema Component Constraint: minInclusive <= maxInclusive
It is an ·error· for the value specified for ·minInclusive· to be greater than the value specified for ·maxInclusive· for the same datatype.
Schema Component Constraint: maxInclusive valid restriction
It is an ·error· if any of the following conditions is true:
1 maxInclusive is among the members of {facets} of {base type definition} and {value} is greater than the {value} of that maxInclusive.
2 maxExclusive is among the members of {facets} of {base type definition} and {value} is greater than or equal to the {value} of that maxExclusive.
3 minInclusive is among the members of {facets} of {base type definition} and {value} is less than the {value} of that minInclusive.
4 minExclusive is among the members of {facets} of {base type definition} and {value} is less than or equal to the {value} of that minExclusive.

4.3.8 maxExclusive

[Definition:]   maxExclusive is the exclusive upper bound of the ·value space· for a datatype with the ·ordered· property.  The value of maxExclusive  must be equal to some value in the ·value space· of the ·base type· or be equal to {value} in {base type definition}.

·maxExclusive· provides for:

  • Constraining a ·value space· to values with a specific exclusive upper bound.
Example
The following is the definition of a ·user-defined· datatype which limits values to integers less than or equal to 100, using ·maxExclusive·.
<simpleType name='less-than-one-hundred-and-one'>
  <restriction base='integer'>
    <maxExclusive value='101'/>
  </restriction>
</simpleType>
Note that the ·value space· of this datatype is identical to the previous one (named 'one-hundred-or-less').
4.3.8.1 The maxExclusive Schema Component
Schema Component: maxExclusive, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
Required.

A value from the ·value space· of the {base type definition}.

{fixed}
An xs:boolean value. Required.

If {fixed} is true, then types for which the current type is the {base type definition} cannot specify a value for maxExclusive other than {value}.

4.3.8.2 XML Representation of maxExclusive Schema Components

The XML representation for a maxExclusive schema component is a <maxExclusive> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: maxExclusive Element Information Item
<maxExclusive
  fixed = boolean : false
  id = ID
  value = anySimpleType
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</maxExclusive>
{value} must be equal to some value in the ·value space· of {base type definition}.
maxExclusive Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.8.3 maxExclusive Validation Rules
Validation Rule: maxExclusive Valid
A value in an ·ordered· ·value space· is facet-valid with respect to ·maxExclusive· if and only if the value is less than {value}, according to the datatype's order relation.
4.3.8.4 Constraints on maxExclusive Schema Components
Schema Component Constraint: maxInclusive and maxExclusive
It is an ·error· for both ·maxInclusive· and ·maxExclusive· to be specified in the same derivation step of a Simple Type Definition.
Schema Component Constraint: minExclusive <= maxExclusive
It is an ·error· for the value specified for ·minExclusive· to be greater than the value specified for ·maxExclusive· for the same datatype.
Schema Component Constraint: maxExclusive valid restriction
It is an ·error· if any of the following conditions is true:
1 maxExclusive is among the members of {facets} of {base type definition} and {value} is greater than the {value} of that maxExclusive.
2 maxInclusive is among the members of {facets} of {base type definition} and {value} is greater than the {value} of that maxInclusive.
3 minInclusive is among the members of {facets} of {base type definition} and {value} is less than or equal to the {value} of that minInclusive.
4 minExclusive is among the members of {facets} of {base type definition} and {value} is less than or equal to the {value} of that minExclusive.

4.3.9 minExclusive

[Definition:]   minExclusive is the exclusive lower bound of the ·value space· for a datatype with the ·ordered· property. The value of minExclusive must be equal to some value in the ·value space· of the ·base type· or be equal to {value} in {base type definition}.

·minExclusive· provides for:

  • Constraining a ·value space· to values with a specific exclusive lower bound.
Example
The following is the definition of a ·user-defined· datatype which limits values to integers greater than or equal to 100, using ·minExclusive·.
<simpleType name='more-than-ninety-nine'>
  <restriction base='integer'>
    <minExclusive value='99'/>
  </restriction>
</simpleType>
Note that the ·value space· of this datatype is identical to the following one (named 'one-hundred-or-more').
4.3.9.1 The minExclusive Schema Component
Schema Component: minExclusive, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
Required.

A value from the ·value space· of the {base type definition}.

{fixed}
An xs:boolean value. Required.

If {fixed} is true, then types for which the current type is the {base type definition} cannot specify a value for minExclusive other than {value}.

4.3.9.2 XML Representation of minExclusive Schema Components

The XML representation for a minExclusive schema component is a <minExclusive> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: minExclusive Element Information Item
<minExclusive
  fixed = boolean : false
  id = ID
  value = anySimpleType
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</minExclusive>
{value} must be equal to some value in the ·value space· of {base type definition}.
minExclusive Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.9.3 minExclusive Validation Rules
Validation Rule: minExclusive Valid
A value in an ·ordered· ·value space· is facet-valid with respect to ·minExclusive· if and only if the value is greater than {value}, according to the datatype's order relation.
4.3.9.4 Constraints on minExclusive Schema Components
Schema Component Constraint: minInclusive and minExclusive
It is an ·error· for both ·minInclusive· and ·minExclusive· to be specified in the same derivation step of a Simple Type Definition.
Schema Component Constraint: minExclusive < maxInclusive
It is an ·error· for the value specified for ·minExclusive· to be greater than or equal to the value specified for ·maxInclusive· for the same datatype.
Schema Component Constraint: minExclusive valid restriction
It is an ·error· if any of the following conditions is true:
1 minExclusive is among the members of {facets} of {base type definition} and {value} is less than the {value} of that minExclusive.
2 minInclusive is among the members of {facets} of {base type definition} and {value} is less than the {value} of that minInclusive.
3 maxInclusive is among the members of {facets} of {base type definition} and {value} is greater than or equal to the {value} of that maxInclusive.
4 maxExclusive is among the members of {facets} of {base type definition} and {value} is greater than or equal to the {value} of that maxExclusive.

4.3.10 minInclusive

[Definition:]   minInclusive is the inclusive lower bound of the ·value space· for a datatype with the ·ordered· property.  The value of minInclusive  must be equal to some value in the ·value space· of the ·base type·.

·minInclusive· provides for:

  • Constraining a ·value space· to values with a specific inclusive lower bound.
Example
The following is the definition of a ·user-defined· datatype which limits values to integers greater than or equal to 100, using ·minInclusive·.
<simpleType name='one-hundred-or-more'>
  <restriction base='integer'>
    <minInclusive value='100'/>
  </restriction>
</simpleType>
4.3.10.1 The minInclusive Schema Component
Schema Component: minInclusive, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
Required.

A value from the ·value space· of the {base type definition}.

{fixed}
An xs:boolean value. Required.

If {fixed} is true, then types for which the current type is the {base type definition} cannot specify a value for minInclusive other than {value}.

4.3.10.2 XML Representation of minInclusive Schema Components

The XML representation for a minInclusive schema component is a <minInclusive> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: minInclusive Element Information Item
<minInclusive
  fixed = boolean : false
  id = ID
  value = anySimpleType
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</minInclusive>
{value} must be equal to some value in the ·value space· of {base type definition}.
minInclusive Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.10.3 minInclusive Validation Rules
Validation Rule: minInclusive Valid
A value in an ·ordered· ·value space· is facet-valid with respect to ·minInclusive· if and only if the value is greater than or equal to {value}, according to the datatype's order relation.
4.3.10.4 Constraints on minInclusive Schema Components
Schema Component Constraint: minInclusive < maxExclusive
It is an ·error· for the value specified for ·minInclusive· to be greater than or equal to the value specified for ·maxExclusive· for the same datatype.
Schema Component Constraint: minInclusive valid restriction
It is an ·error· if any of the following conditions is true:
1 minInclusive is among the members of {facets} of {base type definition} and {value} is less than the {value} of that minInclusive.
2 maxInclusive is among the members of {facets} of {base type definition} and {value} is greater the {value} of that maxInclusive.
3 minExclusive is among the members of {facets} of {base type definition} and {value} is less than or equal to the {value} of that minExclusive.
4 maxExclusive is among the members of {facets} of {base type definition} and {value} is greater than or equal to the {value} of that maxExclusive.

4.3.11 totalDigits

[Definition:]   totalDigits restricts the magnitude and arithmetic precision of values in the ·value spaces· of decimal and datatypes derived from it.

For decimal, if the {value} of totalDigits is t, the effect is to require that values be equal to i / 10n, for some integers i and n, with | i | < 10t and 0 ≤ n ≤ t. This has as a consequence that the values are expressible using at most t digits in decimal notation.

The {value} of totalDigits must be a positiveInteger.

The term 'totalDigits' is chosen to reflect the fact that it restricts the ·value space· to those values that can be represented lexically using at most totalDigits digits in decimal notation, or at most totalDigits digits for the coefficient, in scientific notation.  Note that it does not restrict the ·lexical space· directly; a lexical representation that adds non-significant leading or trailing zero digits is still permitted. It also has no effect on the values NaN, INF, and -INF.

4.3.11.1 The totalDigits Schema Component
Schema Component: totalDigits, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
An xs:positiveInteger value. Required.
{fixed}
An xs:boolean value. Required.

If {fixed} is true, then types for which the current type is the {base type definition} must not specify a value for totalDigits other than {value}.

4.3.11.2 XML Representation of totalDigits Schema Components

The XML representation for a totalDigits schema component is a <totalDigits> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: totalDigits Element Information Item
<totalDigits
  fixed = boolean : false
  id = ID
  value = positiveInteger
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</totalDigits>
totalDigits Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.11.3 totalDigits Validation Rules
Validation Rule: totalDigits Valid
A value v is facet-valid with respect to a totalDigits facet with a {value} of t if and only if v is a decimal value equal to i / 10n, for some integers i and n, with | i | < 10t and 0 ≤ n ≤ t.
4.3.11.4 Constraints on totalDigits Schema Components
Schema Component Constraint: totalDigits valid restriction
It is an ·error· if the ·owner·'s {base type definition} has a totalDigits facet among its {facets} and {value} is greater than the {value} of that totalDigits facet.

4.3.12 fractionDigits

[Definition:]   fractionDigits places an upper limit on the arithmetic precision of decimal values: if the {value} of fractionDigits = f, then the value space is restricted to values equal to i / 10n for some integers i and n and 0 ≤ nf. The value of fractionDigits must be a nonNegativeInteger

The term fractionDigits is chosen to reflect the fact that it restricts the ·value space· to those values that can be represented lexically in decimal notation using at most fractionDigits to the right of the decimal point. Note that it does not restrict the ·lexical space· directly; a lexical representation that adds non-significant leading or trailing zero digits is still permitted.

Example
The following is the definition of a ·user-defined· datatype which could be used to represent the magnitude of a person's body temperature on the Celsius scale. This definition would appear in a schema authored by an "end-user" and shows how to define a datatype by specifying facet values which constrain the range of the ·base type·.
<simpleType name='celsiusBodyTemp'>
  <restriction base='decimal'>
    <fractionDigits value='1'/>
    <minInclusive value='32'/>
	 <maxInclusive value='41.7'/>
  </restriction>
</simpleType>
4.3.12.1 The fractionDigits Schema Component
Schema Component: fractionDigits, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
An xs:nonNegativeInteger value. Required.
{fixed}
An xs:boolean value. Required.

If {fixed} is true, then types for which the current type is the {base type definition} must not specify a value for fractionDigits other than {value}.

4.3.12.2 XML Representation of fractionDigits Schema Components

The XML representation for a fractionDigits schema component is a <fractionDigits> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: fractionDigits Element Information Item
<fractionDigits
  fixed = boolean : false
  id = ID
  value = nonNegativeInteger
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</fractionDigits>
fractionDigits Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.12.3 fractionDigits Validation Rules
Validation Rule: fractionDigits Valid
A value is facet-valid with respect to ·fractionDigits· if and only if that value is equal to i / 10n for integer i and n, with 0 ≤ n{value}.
4.3.12.4 Constraints on fractionDigits Schema Components
Schema Component Constraint: fractionDigits less than or equal to totalDigits
It is an ·error· for the {value} of fractionDigits to be greater than that of totalDigits.
Schema Component Constraint: fractionDigits valid restriction
It is an ·error· if ·fractionDigits· is among the members of {facets} of {base type definition} and {value} is greater than the {value} of that ·fractionDigits·.

4.3.13 Assertions

[Definition:]   Assertions constrain the ·value space· by requiring the values to satisfy specified XPath ([XPath 2.0]) expressions. The value of the assertions facet is a sequence of Assertion components as defined in [XSD 1.1 Part 1: Structures].

Example

The following is the definition of a ·user-defined· datatype which allows all integers but 0 by using an assertion to disallow the value 0.

<simpleType name='nonZeroInteger'>
  <restriction base='integer'>
    <assertion test='$value ne 0'/>
  </restriction>
</simpleType>
Example

The following example defines the datatype "triple", whose ·value space· is the set of integers evenly divisible by three.

<simpleType name='triple'>
  <restriction base='integer'>
    <assertion test='$value mod 3 eq 0'/>
  </restriction>
</simpleType>

The same datatype can be defined without the use of assertions, but the pattern necessary to represent the set of triples is long and error-prone:

<simpleType name='triple'>
  <restriction base='integer'>
    <pattern value=
    "([0369]|[147][0369]*[258]|(([258]|[147][0369]*[147])([0369]|[258][0369]*[147])*([147]|[258][0369]*[258]))*"/>
  </restriction>
</simpleType>

The assertion used in the first version of "triple" is likely to be clearer for many readers of the schema document.

4.3.13.1 The assertions Schema Component
Schema Component: assertions, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}

A sequence of Assertion components.

4.3.13.2 XML Representation of assertions Schema Components

The XML representation for an assertions schema component is one or more <assertion> element information items. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: assertion Element Information Item
<assertion
  id = ID
  test = an XPath expression
  xpathDefaultNamespace = (anyURI | (##defaultNamespace | ##targetNamespace | ##local))
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</assertion>
assertions Schema Component
Property
Representation
 
A sequence whose members are Assertions drawn from the following sources, in order:
1 If the {base type definition} of the ·owner· has an assertions facet among its {facets}, then the Assertions which appear in the {value} of that assertions facet.
2 Assertions corresponding to the <assertion> element information items among the [children] of <restriction>, if any, in document order. For details of the construction of the Assertion components, see section 3.13.2 of [XSD 1.1 Part 1: Structures].
 
The empty sequence.
Note: Annotations specified within an <assertion> element are captured by the individual Assertion component to which it maps.
4.3.13.3 Assertions Validation Rules

The following rule refers to "the nearest built-in" datatype and to the "XDM representation" of a value under a datatype. [Definition:]  For any datatype T, the nearest built-in datatype to T is the first ·built-in· datatype encountered in following the chain of links connecting each datatype to its ·base type·. If T is a ·built-in· datatype, then the nearest built-in datatype of T is T itself; otherwise, it is the nearest built-in datatype of T's ·base type·.

[Definition:]  For any value V and any datatype T, the XDM representation of V under T is defined recursively as follows. Call the XDM representation X. Then
1 If T = ·xs:anySimpleType· or ·xs:anyAtomicType· then X is V, and the dynamic type of X is xs:untypedAtomic.
2 If T . {variety} = atomic, then let T2 be the ·nearest built-in datatype· to T. If V is a member of the ·value space· of T2, then X is V and the dynamic type of X is T2. Otherwise (i.e. if V is not a member of the ·value space· of T2), X is the ·XDM representation· of V under T2 . {base type definition}.
3 If T . {variety} = list, then X is a sequence of atomic values, each atomic value being the ·XDM representation· of the corresponding item in the list V under T . {item type definition}.
4 If T . {variety} = union, then X is the ·XDM representation· of V under the ·active basic member· of V when validated against T. If there is no ·active basic member·, then V has no ·XDM representation· under T.
Note: If the {item type definition} of a ·list· is a ·union·, or the ·active basic member· is a ·list·, then several steps may be necessary before the ·atomic· datatype which serves as the dynamic type of X is found.
Because the {item type definition} of a ·list· is required to be an ·atomic· or ·union· datatype, and the ·active basic member· of a ·union· which accepts the value V is by definition not a ·union·, the recursive rule given above is guaranteed to terminate in a sequence of one or more ·atomic· values, each belonging to an ·atomic· datatype.
Validation Rule: Assertions Valid
A value V is facet-valid with respect to an assertions facet belonging to a simple type T if and only if the {test} property of each Assertion in its {value} evaluates to true under the conditions laid out below, without raising any dynamic error or type error.
Evaluation of {test} is performed as defined in [XPath 2.0], with the following conditions:
1 The XPath expression {test} is evaluated, following the rules given in XPath Evaluation of [XSD 1.1 Part 1: Structures], with the following modifications.
1.1 The in-scope variables in the static context is a set with a single member. The expanded QName of that member has no namespace URI and has 'value' as the local name. The (static) type of the member is anyAtomicType*.
Note: The XDM type label anyAtomicType* simply says that for static typing purposes the variable $value will have a value consisting of a sequence of zero or more atomic values.
1.2 There is no context item for the evaluation of the XPath expression.
Note: In the terminology of [XPath 2.0], the context item is "undefined".
Note: As a consequence the expression '.', or any implicit or explicit reference to the context item, will raise a dynamic error, which will cause the assertion to be treated as false. If an error is detected statically, then the assertion violates the schema component constraint XPath Valid and causes an error to be flagged in the schema.
The variable "$value" can be used to refer to the value being checked.
1.3 There is likewise no value for the context size and the context position in the dynamic context used for evaluation of the assertion.
1.4 The variable values in the dynamic context is a set with a single member. The expanded QName of that member has no namespace URI and 'value' as the local name. The value of the member is the ·XDM representation· of V under T.
1.5 If V has no ·XDM representation· under T, then the XPath expression cannot usefully be evaluated, and V is not facet-valid against the assertions facet of T.
2 The evaluation result is converted to either true or false as if by a call to the XPath fn:boolean function.
4.3.13.4 Constraints on assertions Schema Components
Schema Component Constraint: Valid restriction of assertions
The {value} of the assertions facet on the {base type definition} must be a prefix of the {value}.
Note: For components constructed from XML representations in schema documents, the satisfaction of this constraint is a consequence of the XML mapping rules: any assertion imposed by a simple type definition S will always also be imposed by any type derived from S by ·facet-based restriction·. This constraint ensures that components constructed by other means (so-called "born-binary" components) similarly preserve assertions facets across ·facet-based restriction·.

4.3.14 explicitTimezone

[Definition:]   explicitTimezone is a three-valued facet which can can be used to require or prohibit the time zone offset in date/time datatypes.

Example
The following ·user-defined· datatype accepts only date values without a time zone offset, using the explicitTimezone facet.
<simpleType name='bare-date'>
  <restriction base='date'>
    <explicitTimezone value='prohibited'/>
  </restriction>
</simpleType>
The same effect could also be achieved using the pattern facet, as shown below, but it is somewhat less clear what is going on in this derivation, and it is better practice to use the more straightforward explicitTimezone for this purpose.
<simpleType name='bare-date'>
  <restriction base='date'>
    <pattern value='[^:Z]*'/>
  </restriction>
</simpleType>
4.3.14.1 The explicitTimezone Schema Component
Schema Component: explicitTimezone, a kind of Constraining Facet
{annotations}
A sequence of Annotation components.
{value}
One of {required, prohibited, optional}. Required.
{fixed}
An xs:boolean value. Required.

If {fixed} is true, then datatypes for which the current type is the {base type definition} cannot specify a value for explicitTimezone other than {value}.

Note: It is a consequence of timezone valid restriction (§4.3.14.4) that the value of the explicitTimezone facet cannot be changed unless that value is optional, regardless of whether {fixed} is true or false.  Accordingly, {fixed} is relevant only when {value} is optional.
4.3.14.2 XML Representation of explicitTimezone Schema Components

The XML representation for an explicitTimezone schema component is an <explicitTimezone> element information item. The correspondences between the properties of the information item and properties of the component are as follows:

XML Representation Summary: explicitTimezone Element Information Item
<explicitTimezone
  fixed = boolean : false
  id = ID
  value = NCName
  {any attributes with non-schema namespace . . .}>
  Content: (annotation?)
</explicitTimezone>
explicitTimezone Schema Component
Property
Representation
 
The actual value of the value [attribute]
 
The actual value of the fixed [attribute], if present, otherwise false
 
4.3.14.3 explicitTimezone Validation Rules
Validation Rule: explicitOffset Valid
A dateTime value V is facet-valid with respect to ·explicitTimezone· if and only if one of the following is true
1 The {value} of the facet is required and V has a (non-absent) value for the ·timezoneOffset· property.
2 The {value} of the facet is prohibited and the value for the ·timezoneOffset· property in V is absent.
3 The {value} of the facet is optional.
4.3.14.4 Constraints on explicitTimezone Schema Components
Schema Component Constraint: timezone valid restriction
If the explicitTimezone facet on the {base type definition} has a {value} other than optional, then the {value} of the facet on the ·restriction· must be equal to the {value} on the {base type definition}; otherwise it is an ·error·.
Note: The effect of this rule is to allow datatypes with a explicitTimezone value of optional to be restricted by specifying a value of required or prohibited, and to forbid any other derivations using this facet.

5 Conformance

XSD 1.1: Datatypes is intended to be usable in a variety of contexts.

In the usual case, it will embedded in a host language such as [XSD 1.1 Part 1: Structures], which refers to this specification normatively to define some part of the host language. In some cases, XSD 1.1: Datatypes may be implemented independently of any host language.

Certain aspects of the behavior of conforming processors are described in this specification as ·implementation-defined· or ·implementation-dependent·.
  • [Definition:]  Something which may vary among conforming implementations, but which must be specified by the implementor for each particular implementation, is implementation-defined.
  • [Definition:]  Something which may vary among conforming implementations, is not specified by this or any W3C specification, and is not required to be specified by the implementor for any particular implementation, is implementation-dependent.
Anything described in this specification as ·implementation-defined· or ·implementation-dependent· may be further constrained by the specifications of a host language in which the datatypes and other material specified here are used. A list of implementation-defined and implementation-dependent features can be found in Implementation-defined and implementation-dependent features (normative) (§H)

next sub-section5.1 Host Languages

When XSD 1.1: Datatypes is embedded in a host language, the definition of conformance is specified by the host language, not by this specification. That is, when this specification is implemented in the context of an implementation of a host language, the question of conformance to this specification (separate from the host language) does not arise.

This specification imposes certain constraints on the embedding of XSD 1.1: Datatypes by a host language; these are indicated in the normative text by the use of the verbs 'must', etc., with the phrase "host language" as the subject of the verb.

Note: For convenience, the most important of these constraints are noted here:
  • Host languages should specify that all of the datatypes described here as built-ins are automatically available.
  • Host languages may specify that additional datatypes are also made available automatically.
  • If user-defined datatypes are to be supported in the host language, then the host language must specify how user-defined datatypes are defined and made available for use.

In addition, host languages must require conforming implementations of the host language to obey all of the constraints and rules specified here.

previous sub-section next sub-section5.2 Independent implementations

[Definition:]  Implementations claiming minimal conformance to this specification independent of any host language must do all of the following:
1 Support all the ·built-in· datatypes defined in this specification.
2 Completely and correctly implement all of the ·constraints on schemas· defined in this specification.
3 Completely and correctly implement all of the ·Validation Rules· defined in this specification, when checking the datatype validity of literals against datatypes.
Implementations claiming schema-document-aware conformance to this specification, independent of any host language must be minimally conforming. In addition, they must do all of the following:
1 Accept simple type definitions in the form specified in Datatype components (§4).
2 Completely and correctly implement all of rules governing the XML representation of simple type definitions specified in Datatype components (§4).
3 Map the XML representations of simple type definitions to simple type definition components as specified in the mapping rules given in Datatype components (§4).
Note: The term schema-document aware is used here for parallelism with the corresponding term in [XSD 1.1 Part 1: Structures]. The reference to schema documents may be taken as referring to the fact that schema-document-aware implementations accept the XML representation of simple type definitions found in XSD schema documents. It does not mean that the simple type definitions must themselves be free-standing XML documents, nor that they typically will be.

previous sub-section next sub-section5.3 Conformance of data

Abstract representations of simple type definitions conform to this specification if and only if they obey all of the ·constraints on schemas· defined in this specification.

XML representations of simple type definitions conform to this specification if they obey all of the applicable rules defined in this specification.

Note: Because the conformance of the resulting simple type definition component depends not only on the XML representation of a given simple type definition, but on the properties of its ·base type·, the conformance of an XML representation of a simple type definition does not guarantee that, in the context of other schema components, it will map to a conforming component.

previous sub-section 5.4 Partial Implementation of Infinite Datatypes

Some ·primitive· datatypes defined in this specification have infinite ·value spaces·; no finite implementation can completely handle all their possible values. For some such datatypes, minimum implementation limits are specified below. For other infinite types such as string, hexBinary, and base64Binary, no minimum implementation limits are specified.

When this specification is used in the context of other languages (as it is, for example, by [XSD 1.1 Part 1: Structures]), the host language may specify other minimum implementation limits.

When presented with a literal or value exceeding the capacity of its partial implementation of a datatype, a minimally conforming implementation of this specification will sometimes be unable to determine with certainty whether the value is datatype-valid or not. Sometimes it will be unable to represent the value correctly through its interface to any downstream application.

When either of these is so, a conforming processor must indicate to the user and/or downstream application that it cannot process the input data with assured correctness (much as it would indicate if it ran out of memory). When the datatype validity of a value or literal is uncertain because it exceeds the capacity of a partial implementation, the literal or value must not be treated as invalid, and the unsupported value must not be quietly changed to a supported value.

This specification does not constrain the method used to indicate that a literal or value in the input data has exceeded the capacity of the implementation, or the form such indications take.

·Minimally conforming· processors which set an application- or ·implementation-defined· limit on the size of the values supported must clearly document that limit.

These are the partial-implementation ·minimal conformance· requirements:

A Schema for Schema Documents (Datatypes) (normative)

The XML representation of the datatypes-relevant part of the schema for schema documents is presented here as a normative part of the specification. Independent copies of this material are available in an undated (mutable) version at http://www.w3.org/2009/XMLSchema/datatypes.xsd and in a dated (immutable) version at http://www.w3.org/2012/04/datatypes.xsd — the mutable version will be updated with future revisions of this specification, and the immutable one will not.

Like any other XML document, schema documents may carry XML and document type declarations. An XML declaration and a document type declaration are provided here for convenience. Since this schema document describes the XML Schema language, the targetNamespace attribute on the schema element refers to the XML Schema namespace itself.

Schema documents conforming to this specification may be in XML 1.0 or XML 1.1. Conforming implementations may accept input in XML 1.0 or XML 1.1 or both. See Dependencies on Other Specifications (§1.3).

Schema for Schema Documents (Datatypes)
<?xml version='1.0'?>
<!DOCTYPE xs:schema PUBLIC "-//W3C//DTD XSD 1.1//EN" "XMLSchema.dtd" [

<!--
        Make sure that processors that do not read the external
        subset will know about the various IDs we declare
  -->
        <!ATTLIST xs:simpleType id ID #IMPLIED>
        <!ATTLIST xs:maxExclusive id ID #IMPLIED>
        <!ATTLIST xs:minExclusive id ID #IMPLIED>
        <!ATTLIST xs:maxInclusive id ID #IMPLIED>
        <!ATTLIST xs:minInclusive id ID #IMPLIED>
        <!ATTLIST xs:totalDigits id ID #IMPLIED>
        <!ATTLIST xs:fractionDigits id ID #IMPLIED>
        <!ATTLIST xs:length id ID #IMPLIED>
        <!ATTLIST xs:minLength id ID #IMPLIED>
        <!ATTLIST xs:maxLength id ID #IMPLIED>
        <!ATTLIST xs:enumeration id ID #IMPLIED>
        <!ATTLIST xs:pattern id ID #IMPLIED>
        <!ATTLIST xs:assertion id ID #IMPLIED>
        <!ATTLIST xs:explicitTimezone id ID #IMPLIED>
        <!ATTLIST xs:appinfo id ID #IMPLIED>
        <!ATTLIST xs:documentation id ID #IMPLIED>
        <!ATTLIST xs:list id ID #IMPLIED>
        <!ATTLIST xs:union id ID #IMPLIED>
        ]>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           elementFormDefault="qualified" 
           xml:lang="en"
           targetNamespace="http://www.w3.org/2001/XMLSchema"
           version="datatypes.xsd (rec-20120405)">
  <xs:annotation>
    <xs:documentation source="../datatypes/datatypes.html">
      The schema corresponding to this document is normative,
      with respect to the syntactic constraints it expresses in the
      XML Schema language.  The documentation (within 'documentation'
      elements) below, is not normative, but rather highlights important
      aspects of the W3C Recommendation of which this is a part.

      See below (at the bottom of this document) for information about
      the revision and namespace-versioning policy governing this
      schema document.
    </xs:documentation>
  </xs:annotation>


  <xs:simpleType name="derivationControl">
    <xs:annotation>
      <xs:documentation>
   A utility type, not for public use</xs:documentation>
    </xs:annotation>
    <xs:restriction base="xs:NMTOKEN">
      <xs:enumeration value="substitution"/>
      <xs:enumeration value="extension"/>
      <xs:enumeration value="restriction"/>
      <xs:enumeration value="list"/>
      <xs:enumeration value="union"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:group name="simpleDerivation">
    <xs:choice>
      <xs:element ref="xs:restriction"/>
      <xs:element ref="xs:list"/>
      <xs:element ref="xs:union"/>
    </xs:choice>
  </xs:group>
  <xs:simpleType name="simpleDerivationSet">
    <xs:annotation>
      <xs:documentation>
   #all or (possibly empty) subset of {restriction, extension, union, list}
   </xs:documentation>
      <xs:documentation>
   A utility type, not for public use</xs:documentation>
    </xs:annotation>
    <xs:union>
      <xs:simpleType>
        <xs:restriction base="xs:token">
          <xs:enumeration value="#all"/>
        </xs:restriction>
      </xs:simpleType>
      <xs:simpleType>
        <xs:list>
          <xs:simpleType>
            <xs:restriction base="xs:derivationControl">
              <xs:enumeration value="list"/>
              <xs:enumeration value="union"/>
              <xs:enumeration value="restriction"/>
              <xs:enumeration value="extension"/>
            </xs:restriction>
          </xs:simpleType>
        </xs:list>
      </xs:simpleType>
    </xs:union>
  </xs:simpleType>
  <xs:complexType name="simpleType" abstract="true">
    <xs:complexContent>
      <xs:extension base="xs:annotated">
        <xs:group ref="xs:simpleDerivation"/>
        <xs:attribute name="final" type="xs:simpleDerivationSet"/>
        <xs:attribute name="name" type="xs:NCName">
          <xs:annotation>
            <xs:documentation>
              Can be restricted to required or forbidden
            </xs:documentation>
          </xs:annotation>
        </xs:attribute>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>
  <xs:complexType name="topLevelSimpleType">
    <xs:complexContent>
      <xs:restriction base="xs:simpleType">
        <xs:sequence>
          <xs:element ref="xs:annotation" minOccurs="0"/>
          <xs:group ref="xs:simpleDerivation"/>
        </xs:sequence>
        <xs:attribute name="name" type="xs:NCName" use="required">
          <xs:annotation>
            <xs:documentation>
              Required at the top level
            </xs:documentation>
          </xs:annotation>
        </xs:attribute>
        <xs:anyAttribute namespace="##other" processContents="lax"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
  <xs:complexType name="localSimpleType">
    <xs:complexContent>
      <xs:restriction base="xs:simpleType">
        <xs:sequence>
          <xs:element ref="xs:annotation" minOccurs="0"/>
          <xs:group ref="xs:simpleDerivation"/>
        </xs:sequence>
        <xs:attribute name="name" use="prohibited">
          <xs:annotation>
            <xs:documentation>
              Forbidden when nested
            </xs:documentation>
          </xs:annotation>
        </xs:attribute>
        <xs:attribute name="final" use="prohibited"/>
        <xs:anyAttribute namespace="##other" processContents="lax"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
  <xs:element name="simpleType" type="xs:topLevelSimpleType" id="simpleType">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-simpleType"/>
    </xs:annotation>
  </xs:element>
  <xs:element name="facet" abstract="true">
    <xs:annotation>
      <xs:documentation>
        An abstract element, representing facets in general.
        The facets defined by this spec are substitutable for
        this element, and implementation-defined facets should
        also name this as a substitution-group head.
      </xs:documentation>
    </xs:annotation>
  </xs:element>
  <xs:group name="simpleRestrictionModel">
    <xs:sequence>
      <xs:element name="simpleType" type="xs:localSimpleType" minOccurs="0"/>
      <xs:choice minOccurs="0" 
          maxOccurs="unbounded">
        <xs:element ref="xs:facet"/>
        <xs:any processContents="lax"
            namespace="##other"/>
      </xs:choice>
    </xs:sequence>
  </xs:group>
  <xs:element name="restriction" id="restriction">
    <xs:complexType>
      <xs:annotation>
        <xs:documentation
             source="http://www.w3.org/TR/xmlschema11-2/#element-restriction">
          base attribute and simpleType child are mutually
          exclusive, but one or other is required
        </xs:documentation>
      </xs:annotation>
      <xs:complexContent>
        <xs:extension base="xs:annotated">
          <xs:group ref="xs:simpleRestrictionModel"/>
          <xs:attribute name="base" type="xs:QName" use="optional"/>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>
  <xs:element name="list" id="list">
    <xs:complexType>
      <xs:annotation>
        <xs:documentation
             source="http://www.w3.org/TR/xmlschema11-2/#element-list">
          itemType attribute and simpleType child are mutually
          exclusive, but one or other is required
        </xs:documentation>
      </xs:annotation>
      <xs:complexContent>
        <xs:extension base="xs:annotated">
          <xs:sequence>
            <xs:element name="simpleType" type="xs:localSimpleType"
                        minOccurs="0"/>
          </xs:sequence>
          <xs:attribute name="itemType" type="xs:QName" use="optional"/>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>
  <xs:element name="union" id="union">
    <xs:complexType>
      <xs:annotation>
        <xs:documentation
             source="http://www.w3.org/TR/xmlschema11-2/#element-union">
          memberTypes attribute must be non-empty or there must be
          at least one simpleType child
        </xs:documentation>
      </xs:annotation>
      <xs:complexContent>
        <xs:extension base="xs:annotated">
          <xs:sequence>
            <xs:element name="simpleType" type="xs:localSimpleType"
                        minOccurs="0" maxOccurs="unbounded"/>
          </xs:sequence>
          <xs:attribute name="memberTypes" use="optional">
            <xs:simpleType>
              <xs:list itemType="xs:QName"/>
            </xs:simpleType>
          </xs:attribute>
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>
  <xs:complexType name="facet">
    <xs:complexContent>
      <xs:extension base="xs:annotated">
        <xs:attribute name="value" use="required"/>
        <xs:attribute name="fixed" type="xs:boolean" default="false"
                      use="optional"/>
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>
  <xs:complexType name="noFixedFacet">
    <xs:complexContent>
      <xs:restriction base="xs:facet">
        <xs:sequence>
          <xs:element ref="xs:annotation" minOccurs="0"/>
        </xs:sequence>
        <xs:attribute name="fixed" use="prohibited"/>
        <xs:anyAttribute namespace="##other" processContents="lax"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
  <xs:element name="minExclusive" type="xs:facet"  
    id="minExclusive"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-minExclusive"/>
    </xs:annotation>
  </xs:element>
  <xs:element name="minInclusive" type="xs:facet" 
    id="minInclusive"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-minInclusive"/>
    </xs:annotation>
  </xs:element>
  <xs:element name="maxExclusive" type="xs:facet" 
    id="maxExclusive"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-maxExclusive"/>
    </xs:annotation>
  </xs:element>
  <xs:element name="maxInclusive" type="xs:facet"  
    id="maxInclusive"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-maxInclusive"/>
    </xs:annotation>
  </xs:element>
  <xs:complexType name="numFacet">
    <xs:complexContent>
      <xs:restriction base="xs:facet">
        <xs:sequence>
          <xs:element ref="xs:annotation" minOccurs="0"/>
        </xs:sequence>
        <xs:attribute name="value"  
            type="xs:nonNegativeInteger" use="required"/>
        <xs:anyAttribute namespace="##other" processContents="lax"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="intFacet">
    <xs:complexContent>
      <xs:restriction base="xs:facet">
        <xs:sequence>
          <xs:element ref="xs:annotation" minOccurs="0"/>
        </xs:sequence>
        <xs:attribute name="value" type="xs:integer" use="required"/>
        <xs:anyAttribute namespace="##other" processContents="lax"/>
      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>

  <xs:element name="totalDigits" id="totalDigits"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-totalDigits"/>
    </xs:annotation>
    <xs:complexType>
      <xs:complexContent>
        <xs:restriction base="xs:numFacet">
          <xs:sequence>
            <xs:element ref="xs:annotation" minOccurs="0"/>
          </xs:sequence>
          <xs:attribute name="value" type="xs:positiveInteger" use="required"/>
          <xs:anyAttribute namespace="##other" processContents="lax"/>
        </xs:restriction>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>
  <xs:element name="fractionDigits" type="xs:numFacet"  
    id="fractionDigits"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-fractionDigits"/>
    </xs:annotation>
  </xs:element>

  <xs:element name="length" type="xs:numFacet" id="length"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-length"/>
    </xs:annotation>
  </xs:element>
  <xs:element name="minLength" type="xs:numFacet"  
    id="minLength"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-minLength"/>
    </xs:annotation>
  </xs:element>
  <xs:element name="maxLength" type="xs:numFacet"  
    id="maxLength"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-maxLength"/>
    </xs:annotation>
  </xs:element>
  <xs:element name="enumeration" type="xs:noFixedFacet"  
    id="enumeration"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-enumeration"/>
    </xs:annotation>
  </xs:element>
  <xs:element name="whiteSpace" id="whiteSpace"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-whiteSpace"/>
    </xs:annotation>
    <xs:complexType>
      <xs:complexContent>
        <xs:restriction base="xs:facet">
          <xs:sequence>
            <xs:element ref="xs:annotation" minOccurs="0"/>
          </xs:sequence>
          <xs:attribute name="value" use="required">
            <xs:simpleType>
              <xs:restriction base="xs:NMTOKEN">
                <xs:enumeration value="preserve"/>
                <xs:enumeration value="replace"/>
                <xs:enumeration value="collapse"/>
              </xs:restriction>
            </xs:simpleType>
          </xs:attribute>
          <xs:anyAttribute namespace="##other" processContents="lax"/>
        </xs:restriction>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>
  <xs:element name="pattern" id="pattern"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-pattern"/>
    </xs:annotation>
    <xs:complexType>
      <xs:complexContent>
        <xs:restriction base="xs:noFixedFacet">
          <xs:sequence>
            <xs:element ref="xs:annotation" minOccurs="0"/>
          </xs:sequence>
          <xs:attribute name="value" type="xs:string"  
              use="required"/>
          <xs:anyAttribute namespace="##other"  
              processContents="lax"/>
        </xs:restriction>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>
  <xs:element name="assertion" type="xs:assertion"
              id="assertion" substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-assertion"/>
    </xs:annotation>
  </xs:element>
  <xs:element name="explicitTimezone" id="explicitTimezone"
    substitutionGroup="xs:facet">
    <xs:annotation>
      <xs:documentation
           source="http://www.w3.org/TR/xmlschema11-2/#element-explicitTimezone"/>
    </xs:annotation>
    <xs:complexType>
      <xs:complexContent>
        <xs:restriction base="xs:facet">
          <xs:sequence>
            <xs:element ref="xs:annotation" minOccurs="0"/>
          </xs:sequence>
          <xs:attribute name="value" use="required">
            <xs:simpleType>
              <xs:restriction base="xs:NMTOKEN">
                <xs:enumeration value="optional"/>
                <xs:enumeration value="required"/>
                <xs:enumeration value="prohibited"/>
              </xs:restriction>
            </xs:simpleType>
          </xs:attribute>
          <xs:anyAttribute namespace="##other" processContents="lax"/>
        </xs:restriction>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>

  <xs:annotation>
    <xs:documentation>
      In keeping with the XML Schema WG's standard versioning policy, 
      this schema document will persist at the URI
      http://www.w3.org/2012/04/datatypes.xsd.

      At the date of issue it can also be found at the URI
      http://www.w3.org/2009/XMLSchema/datatypes.xsd.

      The schema document at that URI may however change in the future, 
      in order to remain compatible with the latest version of XSD 
      and its namespace.  In other words, if XSD or the XML Schema 
      namespace change, the version of this document at 
      http://www.w3.org/2009/XMLSchema/datatypes.xsd will change accordingly; 
      the version at http://www.w3.org/2012/04/datatypes.xsd will not change.

      Previous dated (and unchanging) versions of this schema document 
      include:

        http://www.w3.org/2012/01/datatypes.xsd
          (XSD 1.1 Proposed Recommendation)

        http://www.w3.org/2011/07/datatypes.xsd
          (XSD 1.1 Candidate Recommendation)

        http://www.w3.org/2009/04/datatypes.xsd
          (XSD 1.1 Candidate Recommendation)

        http://www.w3.org/2004/10/datatypes.xsd
          (XSD 1.0 Recommendation, Second Edition)

        http://www.w3.org/2001/05/datatypes.xsd
          (XSD 1.0 Recommendation, First Edition)

    </xs:documentation>
  </xs:annotation>



</xs:schema>

B DTD for Datatype Definitions (non-normative)

The DTD for the datatypes-specific aspects of schema documents is given below. Note there is no implication here that schema must be the root element of a document.

DTD for datatype definitions
<!--
        DTD for XML Schemas: Part 2: Datatypes
        
        Id: datatypes.dtd,v 1.1.2.4 2005/01/31 18:40:42 cmsmcq Exp 
        Note this DTD is NOT normative, or even definitive.
  -->

<!--
        This DTD cannot be used on its own, it is intended
        only for incorporation in XMLSchema.dtd, q.v.
  -->

<!-- Define all the element names, with optional prefix -->
<!ENTITY % simpleType "%p;simpleType">
<!ENTITY % restriction "%p;restriction">
<!ENTITY % list "%p;list">
<!ENTITY % union "%p;union">
<!ENTITY % maxExclusive "%p;maxExclusive">
<!ENTITY % minExclusive "%p;minExclusive">
<!ENTITY % maxInclusive "%p;maxInclusive">
<!ENTITY % minInclusive "%p;minInclusive">
<!ENTITY % totalDigits "%p;totalDigits">
<!ENTITY % fractionDigits "%p;fractionDigits">

<!ENTITY % length "%p;length">
<!ENTITY % minLength "%p;minLength">
<!ENTITY % maxLength "%p;maxLength">
<!ENTITY % enumeration "%p;enumeration">
<!ENTITY % whiteSpace "%p;whiteSpace">
<!ENTITY % pattern "%p;pattern">

<!ENTITY % assertion "%p;assertion">

<!ENTITY % explicitTimezone "%p;explicitTimezone">


<!--
        Customization entities for the ATTLIST of each element
        type. Define one of these if your schema takes advantage
        of the anyAttribute='##other' in the schema for schemas
  -->

<!ENTITY % simpleTypeAttrs "">
<!ENTITY % restrictionAttrs "">
<!ENTITY % listAttrs "">
<!ENTITY % unionAttrs "">
<!ENTITY % maxExclusiveAttrs "">
<!ENTITY % minExclusiveAttrs "">
<!ENTITY % maxInclusiveAttrs "">
<!ENTITY % minInclusiveAttrs "">
<!ENTITY % totalDigitsAttrs "">
<!ENTITY % fractionDigitsAttrs "">
<!ENTITY % lengthAttrs "">
<!ENTITY % minLengthAttrs "">
<!ENTITY % maxLengthAttrs "">

<!ENTITY % enumerationAttrs "">
<!ENTITY % whiteSpaceAttrs "">
<!ENTITY % patternAttrs "">
<!ENTITY % assertionAttrs "">
<!ENTITY % explicitTimezoneAttrs "">

<!-- Define some entities for informative use as attribute
        types -->
<!ENTITY % URIref "CDATA">
<!ENTITY % XPathExpr "CDATA">
<!ENTITY % QName "NMTOKEN">
<!ENTITY % QNames "NMTOKENS">
<!ENTITY % NCName "NMTOKEN">
<!ENTITY % nonNegativeInteger "NMTOKEN">
<!ENTITY % boolean "(true|false)">
<!ENTITY % simpleDerivationSet "CDATA">
<!--
        #all or space-separated list drawn from derivationChoice
  -->

<!--
        Note that the use of 'facet' below is less restrictive
        than is really intended:  There should in fact be no
        more than one of each of minInclusive, minExclusive,
        maxInclusive, maxExclusive, totalDigits, fractionDigits,
        length, maxLength, minLength within datatype,
        and the min- and max- variants of Inclusive and Exclusive
        are mutually exclusive. On the other hand,  pattern and
        enumeration and assertion may repeat.
  -->
<!ENTITY % minBound "(%minInclusive; | %minExclusive;)">
<!ENTITY % maxBound "(%maxInclusive; | %maxExclusive;)">
<!ENTITY % bounds "%minBound; | %maxBound;">
<!ENTITY % numeric "%totalDigits; | %fractionDigits;"> 
<!ENTITY % ordered "%bounds; | %numeric;">
<!ENTITY % unordered
   "%pattern; | %enumeration; | %whiteSpace; | %length; |
   %maxLength; | %minLength; | %assertion;
   | %explicitTimezone;">
<!ENTITY % implementation-defined-facets "">
<!ENTITY % facet "%ordered; | %unordered; %implementation-defined-facets;">
<!ENTITY % facetAttr 
        "value CDATA #REQUIRED
        id ID #IMPLIED">
<!ENTITY % fixedAttr "fixed %boolean; #IMPLIED">
<!ENTITY % facetModel "(%annotation;)?">
<!ELEMENT %simpleType;
        ((%annotation;)?, (%restriction; | %list; | %union;))>
<!ATTLIST %simpleType;
    name      %NCName; #IMPLIED
    final     %simpleDerivationSet; #IMPLIED
    id        ID       #IMPLIED
    %simpleTypeAttrs;>
<!-- name is required at top level -->
<!ELEMENT %restriction; ((%annotation;)?,
                         (%restriction1; |
                          ((%simpleType;)?,(%facet;)*)),
                         (%attrDecls;))>
<!ATTLIST %restriction;
    base      %QName;                  #IMPLIED
    id        ID       #IMPLIED
    %restrictionAttrs;>
<!--
        base and simpleType child are mutually exclusive,
        one is required.

        restriction is shared between simpleType and
        simpleContent and complexContent (in XMLSchema.xsd).
        restriction1 is for the latter cases, when this
        is restricting a complex type, as is attrDecls.
  -->
<!ELEMENT %list; ((%annotation;)?,(%simpleType;)?)>
<!ATTLIST %list;
    itemType      %QName;             #IMPLIED
    id        ID       #IMPLIED
    %listAttrs;>
<!--
        itemType and simpleType child are mutually exclusive,
        one is required
  -->
<!ELEMENT %union; ((%annotation;)?,(%simpleType;)*)>
<!ATTLIST %union;
    id            ID       #IMPLIED
    memberTypes   %QNames;            #IMPLIED
    %unionAttrs;>
<!--
        At least one item in memberTypes or one simpleType
        child is required
  -->

<!ELEMENT %maxExclusive; %facetModel;>
<!ATTLIST %maxExclusive;
        %facetAttr;
        %fixedAttr;
        %maxExclusiveAttrs;>
<!ELEMENT %minExclusive; %facetModel;>
<!ATTLIST %minExclusive;
        %facetAttr;
        %fixedAttr;
        %minExclusiveAttrs;>

<!ELEMENT %maxInclusive; %facetModel;>
<!ATTLIST %maxInclusive;
        %facetAttr;
        %fixedAttr;
        %maxInclusiveAttrs;>
<!ELEMENT %minInclusive; %facetModel;>
<!ATTLIST %minInclusive;
        %facetAttr;
        %fixedAttr;
        %minInclusiveAttrs;>

<!ELEMENT %totalDigits; %facetModel;>
<!ATTLIST %totalDigits;
        %facetAttr;
        %fixedAttr;
        %totalDigitsAttrs;>
<!ELEMENT %fractionDigits; %facetModel;>
<!ATTLIST %fractionDigits;
        %facetAttr;
        %fixedAttr;
        %fractionDigitsAttrs;>

<!ELEMENT %length; %facetModel;>
<!ATTLIST %length;
        %facetAttr;
        %fixedAttr;
        %lengthAttrs;>
<!ELEMENT %minLength; %facetModel;>
<!ATTLIST %minLength;
        %facetAttr;
        %fixedAttr;
        %minLengthAttrs;>
<!ELEMENT %maxLength; %facetModel;>
<!ATTLIST %maxLength;
        %facetAttr;
        %fixedAttr;
        %maxLengthAttrs;>

<!-- This one can be repeated -->
<!ELEMENT %enumeration; %facetModel;>
<!ATTLIST %enumeration;
        %facetAttr;
        %enumerationAttrs;>

<!ELEMENT %whiteSpace; %facetModel;>
<!ATTLIST %whiteSpace;
        %facetAttr;
        %fixedAttr;
        %whiteSpaceAttrs;>

<!-- This one can be repeated -->
<!ELEMENT %pattern; %facetModel;>
<!ATTLIST %pattern;
        %facetAttr;
        %patternAttrs;>

<!ELEMENT %assertion; %facetModel;>
<!ATTLIST %assertion;
        %facetAttr;
        %assertionAttrs;>

<!ELEMENT %explicitTimezone; %facetModel;>
<!ATTLIST %explicitTimezone;
        %facetAttr;
        %explicitTimezoneAttrs;>

C Illustrative XML representations for the built-in simple type definitions

next sub-sectionC.1 Illustrative XML representations for the built-in primitive type definitions

The following, although in the form of a schema document, does not conform to the rules for schema documents defined in this specification. It contains explicit XML representations of the primitive datatypes which need not be declared in a schema document, since they are automatically included in every schema, and indeed must not be declared in a schema document, since it is forbidden to try to derive types with anyAtomicType as the base type definition. It is included here as a form of documentation.

The (not a) schema document for primitive built-in type definitions
<?xml version='1.0'?>
<!DOCTYPE xs:schema SYSTEM "../namespace/XMLSchema.dtd" [

<!--
     keep this schema XML1.0 DTD valid
  -->
        <!ENTITY % schemaAttrs 'xmlns:hfp CDATA #IMPLIED'>

        <!ELEMENT hfp:hasFacet EMPTY>
        <!ATTLIST hfp:hasFacet
                name NMTOKEN #REQUIRED>

        <!ELEMENT hfp:hasProperty EMPTY>
        <!ATTLIST hfp:hasProperty
                name NMTOKEN #REQUIRED
                value CDATA #REQUIRED>
]>
<xs:schema
  xmlns:hfp="http://www.w3.org/2001/XMLSchema-hasFacetAndProperty" 
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  elementFormDefault="qualified" 
  xml:lang="en" 
  targetNamespace="http://www.w3.org/2001/XMLSchema">

  <xs:annotation>
    <xs:documentation>
      This document contains XML elements which look like 
      definitions for the primitive datatypes.  These definitions are for
      information only; the real built-in definitions are magic.
    </xs:documentation>
    <xs:documentation>
      For each built-in datatype in this schema (both primitive and
      derived) can be uniquely addressed via a URI constructed
      as follows:
        1) the base URI is the URI of the XML Schema namespace
        2) the fragment identifier is the name of the datatype

      For example, to address the int datatype, the URI is:

        http://www.w3.org/2001/XMLSchema#int

      Additionally, each facet definition element can be uniquely
      addressed via a URI constructed as follows:
        1) the base URI is the URI of the XML Schema namespace
        2) the fragment identifier is the name of the facet

      For example, to address the maxInclusive facet, the URI is:

        http://www.w3.org/2001/XMLSchema#maxInclusive

      Additionally, each facet usage in a built-in datatype definition
      can be uniquely addressed via a URI constructed as follows:
        1) the base URI is the URI of the XML Schema namespace
        2) the fragment identifier is the name of the datatype, followed
           by a period (".") followed by the name of the facet

      For example, to address the usage of the maxInclusive facet in
      the definition of int, the URI is:

        http://www.w3.org/2001/XMLSchema#int.maxInclusive

    </xs:documentation>
  </xs:annotation>
  <xs:simpleType name="string" id="string">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="length"/>
        <hfp:hasFacet name="minLength"/>
        <hfp:hasFacet name="maxLength"/>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="false"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#string"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace value="preserve" id="string.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="boolean" id="boolean">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="false"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="finite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#boolean"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="boolean.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="float" id="float">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="true"/>
        <hfp:hasProperty name="cardinality" value="finite"/>
        <hfp:hasProperty name="numeric" value="true"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#float"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="float.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="double" id="double">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="true"/>
        <hfp:hasProperty name="cardinality" value="finite"/>
        <hfp:hasProperty name="numeric" value="true"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#double"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="double.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="decimal" id="decimal">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="totalDigits"/>
        <hfp:hasFacet name="fractionDigits"/>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="total"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="true"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#decimal"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="decimal.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="duration" id="duration">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#duration"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="duration.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="dateTime" id="dateTime">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasFacet name="explicitTimezone"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#dateTime"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="dateTime.whiteSpace"/>
      <xs:explicitTimezone value="optional" id="dateTime.explicitTimezone"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="time" id="time">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasFacet name="explicitTimezone"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#time"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="time.whiteSpace"/>
      <xs:explicitTimezone value="optional" id="time.explicitTimezone"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="date" id="date">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasFacet name="explicitTimezone"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#date"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="date.whiteSpace"/>
      <xs:explicitTimezone value="optional" id="date.explicitTimezone"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="gYearMonth" id="gYearMonth">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasFacet name="explicitTimezone"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#gYearMonth"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="gYearMonth.whiteSpace"/>
      <xs:explicitTimezone value="optional" id="gYearMonth.explicitTimezone"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="gYear" id="gYear">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasFacet name="explicitTimezone"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#gYear"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="gYear.whiteSpace"/>
      <xs:explicitTimezone value="optional" id="gYear.explicitTimezone"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="gMonthDay" id="gMonthDay">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasFacet name="explicitTimezone"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#gMonthDay"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="gMonthDay.whiteSpace"/>
      <xs:explicitTimezone value="optional" id="gMonthDay.explicitTimezone"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="gDay" id="gDay">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasFacet name="explicitTimezone"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#gDay"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="gDay.whiteSpace"/>
      <xs:explicitTimezone value="optional" id="gDay.explicitTimezone"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="gMonth" id="gMonth">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="maxInclusive"/>
        <hfp:hasFacet name="maxExclusive"/>
        <hfp:hasFacet name="minInclusive"/>
        <hfp:hasFacet name="minExclusive"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasFacet name="explicitTimezone"/>
        <hfp:hasProperty name="ordered" value="partial"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#gMonth"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="gMonth.whiteSpace"/>
      <xs:explicitTimezone value="optional" id="gMonth.explicitTimezone"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="hexBinary" id="hexBinary">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="length"/>
        <hfp:hasFacet name="minLength"/>
        <hfp:hasFacet name="maxLength"/>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="false"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#hexBinary"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="hexBinary.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="base64Binary" id="base64Binary">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="length"/>
        <hfp:hasFacet name="minLength"/>
        <hfp:hasFacet name="maxLength"/>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="false"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#base64Binary"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="base64Binary.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="anyURI" id="anyURI">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="length"/>
        <hfp:hasFacet name="minLength"/>
        <hfp:hasFacet name="maxLength"/>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="false"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#anyURI"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="anyURI.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="QName" id="QName">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="length"/>
        <hfp:hasFacet name="minLength"/>
        <hfp:hasFacet name="maxLength"/>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="false"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#QName"/>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="QName.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="NOTATION" id="NOTATION">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="length"/>
        <hfp:hasFacet name="minLength"/>
        <hfp:hasFacet name="maxLength"/>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="false"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#NOTATION"/>
      <xs:documentation>
        NOTATION cannot be used directly in a schema; rather a type
        must be derived from it by specifying at least one enumeration
        facet whose value is the name of a NOTATION declared in the
        schema.
      </xs:documentation>
    </xs:annotation>
    <xs:restriction base="xs:anyAtomicType">
      <xs:whiteSpace fixed="true" value="collapse" id="NOTATION.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
</xs:schema>

previous sub-section C.2 Illustrative XML representations for the built-in ordinary type definitions

The following, although in the form of a schema document, contains XML representations of components already present in all schemas by definition. It is included here as a form of documentation.

Note: These datatypes do not need to be declared in a schema document, since they are automatically included in every schema.
Issue (B-1933):
It is an open question whether this and similar XML documents should be accepted or rejected by software conforming to this specification. The XML Schema Working Group expects to resolve this question in connection with its work on issues relating to schema composition.
In the meantime, some existing schema processors will accept declarations for them; other existing processors will reject such declarations as duplicates.
Illustrative schema document for derived built-in type definitions
<?xml version='1.0'?>
<!DOCTYPE xs:schema SYSTEM "../namespace/XMLSchema.dtd" [

<!--
     keep this schema XML1.0 DTD valid
  -->
        <!ENTITY % schemaAttrs 'xmlns:hfp CDATA #IMPLIED'>

        <!ELEMENT hfp:hasFacet EMPTY>
        <!ATTLIST hfp:hasFacet
                name NMTOKEN #REQUIRED>

        <!ELEMENT hfp:hasProperty EMPTY>
        <!ATTLIST hfp:hasProperty
                name NMTOKEN #REQUIRED
                value CDATA #REQUIRED>

]>
<xs:schema
  xmlns:hfp="http://www.w3.org/2001/XMLSchema-hasFacetAndProperty"
  xmlns:xs="http://www.w3.org/2001/XMLSchema"
  elementFormDefault="qualified" 
  xml:lang="en" 
  targetNamespace="http://www.w3.org/2001/XMLSchema">
 <xs:annotation>
    <xs:documentation>
      This document contains XML representations for the 
     ordinary non-primitive built-in datatypes
    </xs:documentation>
  </xs:annotation>
  <xs:simpleType name="normalizedString" id="normalizedString">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#normalizedString"/>
    </xs:annotation>
    <xs:restriction base="xs:string">
      <xs:whiteSpace value="replace" id="normalizedString.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="token" id="token">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#token"/>
    </xs:annotation>
    <xs:restriction base="xs:normalizedString">
      <xs:whiteSpace value="collapse" id="token.whiteSpace"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="language" id="language">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#language"/>
    </xs:annotation>
    <xs:restriction base="xs:token">
      <xs:pattern value="[a-zA-Z]{1,8}(-[a-zA-Z0-9]{1,8})*" id="language.pattern">
        <xs:annotation>
          <xs:documentation source="http://www.ietf.org/rfc/bcp/bcp47.txt">
            pattern specifies the content of section 2.12 of XML 1.0e2
            and RFC 3066 (Revised version of RFC 1766).  N.B. RFC 3066 is now
            obsolete; the grammar of RFC4646 is more restrictive.  So strict
            conformance to the rules for language codes requires extra checking
            beyond validation against this type.
          </xs:documentation>
        </xs:annotation>
      </xs:pattern>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="IDREFS" id="IDREFS">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="length"/>
        <hfp:hasFacet name="minLength"/>
        <hfp:hasFacet name="maxLength"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="false"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#IDREFS"/>
    </xs:annotation>
    <xs:restriction>
      <xs:simpleType>
        <xs:list itemType="xs:IDREF"/>
      </xs:simpleType>
      <xs:minLength value="1" id="IDREFS.minLength"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="ENTITIES" id="ENTITIES">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="length"/>
        <hfp:hasFacet name="minLength"/>
        <hfp:hasFacet name="maxLength"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="false"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#ENTITIES"/>
    </xs:annotation>
    <xs:restriction>
      <xs:simpleType>
        <xs:list itemType="xs:ENTITY"/>
      </xs:simpleType>
      <xs:minLength value="1" id="ENTITIES.minLength"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="NMTOKEN" id="NMTOKEN">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#NMTOKEN"/>
    </xs:annotation>
    <xs:restriction base="xs:token">
      <xs:pattern value="\c+" id="NMTOKEN.pattern">
        <xs:annotation>
          <xs:documentation source="http://www.w3.org/TR/REC-xml#NT-Nmtoken">
            pattern matches production 7 from the XML spec
          </xs:documentation>
        </xs:annotation>
      </xs:pattern>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="NMTOKENS" id="NMTOKENS">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasFacet name="length"/>
        <hfp:hasFacet name="minLength"/>
        <hfp:hasFacet name="maxLength"/>
        <hfp:hasFacet name="enumeration"/>
        <hfp:hasFacet name="whiteSpace"/>
        <hfp:hasFacet name="pattern"/>
        <hfp:hasFacet name="assertions"/>
        <hfp:hasProperty name="ordered" value="false"/>
        <hfp:hasProperty name="bounded" value="false"/>
        <hfp:hasProperty name="cardinality" value="countably infinite"/>
        <hfp:hasProperty name="numeric" value="false"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#NMTOKENS"/>
    </xs:annotation>
    <xs:restriction>
      <xs:simpleType>
        <xs:list itemType="xs:NMTOKEN"/>
      </xs:simpleType>
      <xs:minLength value="1" id="NMTOKENS.minLength"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="Name" id="Name">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#Name"/>
    </xs:annotation>
    <xs:restriction base="xs:token">
      <xs:pattern value="\i\c*" id="Name.pattern">
        <xs:annotation>
          <xs:documentation source="http://www.w3.org/TR/REC-xml#NT-Name">
            pattern matches production 5 from the XML spec
          </xs:documentation>
        </xs:annotation>
      </xs:pattern>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="NCName" id="NCName">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#NCName"/>
    </xs:annotation>
    <xs:restriction base="xs:Name">
      <xs:pattern value="[\i-[:]][\c-[:]]*" id="NCName.pattern">
        <xs:annotation>
          <xs:documentation source="http://www.w3.org/TR/REC-xml-names/#NT-NCName">
            pattern matches production 4 from the Namespaces in XML spec
          </xs:documentation>
        </xs:annotation>
      </xs:pattern>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="ID" id="ID">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#ID"/>
    </xs:annotation>
    <xs:restriction base="xs:NCName"/>
  </xs:simpleType>
  <xs:simpleType name="IDREF" id="IDREF">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#IDREF"/>
    </xs:annotation>
    <xs:restriction base="xs:NCName"/>
  </xs:simpleType>
  <xs:simpleType name="ENTITY" id="ENTITY">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#ENTITY"/>
    </xs:annotation>
    <xs:restriction base="xs:NCName"/>
  </xs:simpleType>
  <xs:simpleType name="integer" id="integer">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#integer"/>
    </xs:annotation>
    <xs:restriction base="xs:decimal">
      <xs:fractionDigits fixed="true" value="0" id="integer.fractionDigits"/>
      <xs:pattern value="[\-+]?[0-9]+" id="integer.pattern"/>
      
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="nonPositiveInteger" id="nonPositiveInteger">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#nonPositiveInteger"/>
    </xs:annotation>
    <xs:restriction base="xs:integer">
      <xs:maxInclusive value="0" id="nonPositiveInteger.maxInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="negativeInteger" id="negativeInteger">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#negativeInteger"/>
    </xs:annotation>
    <xs:restriction base="xs:nonPositiveInteger">
      <xs:maxInclusive value="-1" id="negativeInteger.maxInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="long" id="long">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasProperty name="bounded" value="true"/>
        <hfp:hasProperty name="cardinality" value="finite"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#long"/>
    </xs:annotation>
    <xs:restriction base="xs:integer">
      <xs:minInclusive value="-9223372036854775808" id="long.minInclusive"/>
      <xs:maxInclusive value="9223372036854775807" id="long.maxInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="int" id="int">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#int"/>
    </xs:annotation>
    <xs:restriction base="xs:long">
      <xs:minInclusive value="-2147483648" id="int.minInclusive"/>
      <xs:maxInclusive value="2147483647" id="int.maxInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="short" id="short">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#short"/>
    </xs:annotation>
    <xs:restriction base="xs:int">
      <xs:minInclusive value="-32768" id="short.minInclusive"/>
      <xs:maxInclusive value="32767" id="short.maxInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="byte" id="byte">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#byte"/>
    </xs:annotation>
    <xs:restriction base="xs:short">
      <xs:minInclusive value="-128" id="byte.minInclusive"/>
      <xs:maxInclusive value="127" id="byte.maxInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="nonNegativeInteger" id="nonNegativeInteger">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#nonNegativeInteger"/>
    </xs:annotation>
    <xs:restriction base="xs:integer">
      <xs:minInclusive value="0" id="nonNegativeInteger.minInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="unsignedLong" id="unsignedLong">
    <xs:annotation>
      <xs:appinfo>
        <hfp:hasProperty name="bounded" value="true"/>
        <hfp:hasProperty name="cardinality" value="finite"/>
      </xs:appinfo>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#unsignedLong"/>
    </xs:annotation>
    <xs:restriction base="xs:nonNegativeInteger">
      <xs:maxInclusive value="18446744073709551615" id="unsignedLong.maxInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="unsignedInt" id="unsignedInt">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#unsignedInt"/>
    </xs:annotation>
    <xs:restriction base="xs:unsignedLong">
      <xs:maxInclusive value="4294967295" id="unsignedInt.maxInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="unsignedShort" id="unsignedShort">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#unsignedShort"/>
    </xs:annotation>
    <xs:restriction base="xs:unsignedInt">
      <xs:maxInclusive value="65535" id="unsignedShort.maxInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="unsignedByte" id="unsignedByte">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#unsignedByte"/>
    </xs:annotation>
    <xs:restriction base="xs:unsignedShort">
      <xs:maxInclusive value="255" id="unsignedByte.maxInclusive"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="positiveInteger" id="positiveInteger">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#positiveInteger"/>
    </xs:annotation>
    <xs:restriction base="xs:nonNegativeInteger">
      <xs:minInclusive value="1" id="positiveInteger.minInclusive"/>
    </xs:restriction>
  </xs:simpleType>

  <xs:simpleType name="yearMonthDuration">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#yearMonthDuration">
        This type includes just those durations expressed in years and months.
        Since the pattern given excludes days, hours, minutes, and seconds,
        the values of this type have a seconds property of zero.  They are
        totally ordered.
      </xs:documentation>
    </xs:annotation>
    <xs:restriction base="xs:duration">
      <xs:pattern id="yearMonthDuration.pattern" value="[^DT]*"/>
    </xs:restriction>
  </xs:simpleType>
  <xs:simpleType name="dayTimeDuration">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#dayTimeDuration">
        This type includes just those durations expressed in days, hours, minutes, and seconds.
        The pattern given excludes years and months, so the values of this type 
        have a months property of zero.  They are totally ordered.
      </xs:documentation>
    </xs:annotation>
    <xs:restriction base="xs:duration">
      <xs:pattern id="dayTimeDuration.pattern" value="[^YM]*(T.*)?"/>
     </xs:restriction>
  </xs:simpleType>
    <xs:simpleType name="dateTimeStamp" id="dateTimeStamp">
    <xs:annotation>
      <xs:documentation source="http://www.w3.org/TR/xmlschema11-2/#dateTimeStamp">
        This datatype includes just those dateTime values Whose explicitTimezone
        is present.  They are totally ordered.
      </xs:documentation>
    </xs:annotation>
    <xs:restriction base="xs:dateTime">
      <xs:explicitTimezone fixed="true"
        id="dateTimeStamp.explicitTimezone" value="required"/>
     </xs:restriction>
  </xs:simpleType>

</xs:schema>

D Built-up Value Spaces

Some datatypes, such as integer, describe well-known mathematically abstract systems.  Others, such as the date/time datatypes, describe "real-life", "applied" systems.  Certain of the systems described by datatypes, both abstract and applied, have values in their value spaces most easily described as things having several properties, which in turn have values which are in some sense "primitive" or are from the value spaces of simpler datatypes.

In this document, the arguments to functions are assumed to be "call by value" unless explicitly noted to the contrary, meaning that if the argument is modified during the processing of the algorithm, that modification is not reflected in the "outside world".  On the other hand, the arguments to procedures are assumed to be "call by location", meaning that modifications are so reflected, since that is the only way the processing of the algorithm can have any effect.

Properties always have values.  [Definition:]  An optional property is permitted but not required to have the distinguished value absent.

[Definition:]  Throughout this specification, the value absent is used as a distinguished value to indicate that a given instance of a property "has no value" or "is absent".  This should not be interpreted as constraining implementations, as for instance between using a null value for such properties or not representing them at all.

Those values that are more primitive, and are used (among other things) herein to construct object value spaces but which we do not explicitly define are described here:
  • A number (without precision) is an ordinary mathematical number; 1, 1.0, and 1.000000000000 are the same number.  The decimal numbers and integers generally used in the algorithms of appendix Function Definitions (§E) are such ordinary numbers, not carrying precision.
  • [Definition:]  A special value is an object whose only relevant properties for purposes of this specification are that it is distinct from, and unequal to, any other values (special or otherwise).  A few special values in different value spaces (e.g. positiveInfinity, negativeInfinity, and notANumber in float and double) share names.  Thus, special values can be distinguished from each other in the general case by considering both the name and the primitive datatype of the value; in some cases, of course, the name alone suffices to identify the value uniquely.
    Note: In the case of float and double, the ·special values· are members of the datatype's ·value space·

next sub-sectionD.1 Numerical Values

The following standard operators are defined here in case the reader is unsure of their definition:
  • [Definition:]  If m and n are numbers, then m div n is the greatest integer less than or equal to m / n .
  • [Definition:]  If m and n are numbers, then m mod n is  m − n × ( m ·div· n) .
Note: n ·div· 1  is a convenient and short way of expressing "the greatest integer less than or equal to n".

D.1.1 Exact Lexical Mappings

Numerals and Fragments Thereof
[45]   digit ::= [0-9]
[46]   unsignedNoDecimalPtNumeral ::= digit+
[47]   noDecimalPtNumeral ::= ('+' | '-')? unsignedNoDecimalPtNumeral
[48]   fracFrag ::= digit+
[49]   unsignedDecimalPtNumeral ::= (unsignedNoDecimalPtNumeral '.fracFrag?) | ('.fracFrag)
[50]   unsignedFullDecimalPtNumeral ::= unsignedNoDecimalPtNumeral '.fracFrag
[51]   decimalPtNumeral ::= ('+' | '-')? unsignedDecimalPtNumeral
[52]   unsignedScientificNotationNumeral ::= (unsignedNoDecimalPtNumeral | unsignedDecimalPtNumeral) ('e' | 'E') noDecimalPtNumeral
[53]   scientificNotationNumeral ::= ('+' | '-')? unsignedScientificNotationNumeral
Generic Numeral-to-Number Lexical Mappings
·unsignedNoDecimalMap· (N) → integer
Maps an unsignedNoDecimalPtNumeral to its numerical value.
·noDecimalMap· (N) → integer
Maps an noDecimalPtNumeral to its numerical value.
·unsignedDecimalPtMap· (D) → decimal number
Maps an unsignedDecimalPtNumeral to its numerical value.
·decimalPtMap· (N) → decimal number
Maps a decimalPtNumeral to its numerical value.
·scientificMap· (N) → decimal number
Maps a scientificNotationNumeral to its numerical value.
Some numerical datatypes include some or all of three non-numerical ·special values·: positiveInfinity, negativeInfinity, and notANumber.  Their lexical spaces include non-numeral lexical representations for these non-numeric values:
Special Non-numerical Lexical Representations Used With Numerical Datatypes
[54]   minimalNumericalSpecialRep ::= 'INF' | '-INF' | 'NaN'
[55]   numericalSpecialRep ::= '+INF' | minimalNumericalSpecialRep
Lexical Mapping for Non-numerical ·Special Values· Used With Numerical Datatypes
Maps the ·lexical representations· of ·special values· used with some numerical datatypes to those ·special values·.
Canonical Mapping for Non-numerical ·Special Values· Used with Numerical Datatypes
Maps the ·special values· used with some numerical datatypes to their ·canonical representations·.

previous sub-section D.2 Date/time Values

        D.2.1 The Seven-property Model
        D.2.2 Lexical Mappings

There are several different primitive but related datatypes defined in the specification which pertain to various combinations of dates and times, and parts thereof.  They all use related value-space models, which are described in detail in this section.  It is not difficult for a casual reader of the descriptions of the individual datatypes elsewhere in this specification to misunderstand some of the details of just what the datatypes are intended to represent, so more detail is presented here in this section.

All of the value spaces for dates and times described here represent moments or periods of time in Universal Coordinated Time (UTC).  [Definition:]  Universal Coordinated Time (UTC) is an adaptation of TAI which closely approximates UT1 by adding ·leap-seconds· to selected ·UTC· days.

[Definition:]  A leap-second is an additional second added to the last day of December, June, October, or March, when such an adjustment is deemed necessary by the International Earth Rotation and Reference Systems Service in order to keep ·UTC· within 0.9 seconds of observed astronomical time.  When leap seconds are introduced, the last minute in the day has more than sixty seconds.  In theory leap seconds can also be removed from a day, but this has not yet occurred. (See [International Earth Rotation Service (IERS)], [ITU-R TF.460-6].) Leap seconds are not supported by the types defined here.

Because the dateTime type and other date- and time-related types defined in this specification do not support leap seconds, there are portions of the ·UTC· timeline which cannot be represented by values of these types. Users whose applications require that leap seconds be represented and that date/time arithmetic take historically occurring leap seconds into account will wish to make appropriate adjustments at the application level, or to use other types.

D.2.1 The Seven-property Model

There are two distinct ways to model moments in time:  either by tracking their year, month, day, hour, minute and second (with fractional seconds as needed), or by tracking their time (measured generally in seconds or days) from some starting moment.  Each has its advantages.  The two are isomorphic.  For definiteness, we choose to model the first using five integer and one decimal number properties.  We superimpose the second by providing one decimal number-valued function which gives the corresponding count of seconds from zero (the "time on the time line").

There is also a seventh integer property which specifies the time zone offset as the number of minutes of offset from UTC.  Values for the six primary properties are always stored in their "local" values (the values shown in the lexical representations), rather than converted to ·UTC·.
an integer
an integer between 1 and 12 inclusive
an integer between 1 and 31 inclusive, possibly restricted further depending on ·month· and ·year·
an integer between 0 and 23 inclusive
an integer between 0 and 59 inclusive
a decimal number greater than or equal to 0 and less than 60.
an ·optional· integer between −840 and 840 inclusive

Non-negative values of the properties map to the years, months, days of month, etc. of the Gregorian calendar in the obvious way. Values less than 1582 in the ·year· property represent years in the "proleptic Gregorian calendar". A value of zero in the ·year· property represents the year 1 BCE; a value of −1 represents the year 2 BCE, −2 is 3 BCE, etc.

Note: In version 1.0 of this specification, the ·year· property was not permitted to have the value zero. The year before the year 1 in the proleptic Gregorian calendar, traditionally referred to as 1 BC or as 1 BCE, was represented by a ·year· value of −1, 2 BCE by −2, and so forth. Of course, many, perhaps most, references to 1 BCE (or 1 BC) actually refer not to a year in the proleptic Gregorian calendar but to a year in the Julian or "old style" calendar; the two correspond approximately but not exactly to each other.
In this version of this specification, two changes are made in order to agree with existing usage. First, ·year· is permitted to have the value zero. Second, the interpretation of ·year· values is changed accordingly: a ·year· value of zero represents 1 BCE, −1 represents 2 BCE, etc. This representation simplifies interval arithmetic and leap-year calculation for dates before the common era (which may be why astronomers and others interested in such calculations with the proleptic Gregorian calendar have adopted it), and is consistent with the current edition of [ISO 8601].
Note that 1 BCE, 5 BCE, and so on (years 0000, −0004, etc. in the lexical representation defined here) are leap years in the proleptic Gregorian calendar used for the date/time datatypes defined here. Version 1.0 of this specification was unclear about the treatment of leap years before the common era. If existing schemas or data specify dates of 29 February for any years before the common era, then some values giving a date of 29 February which were valid under a plausible interpretation of XSD 1.0 will be invalid under this specification, and some which were invalid will be valid. With that possible exception, schemas and data valid under the old interpretation remain valid under the new.

The model just described is called herein the "seven-property" model for date/time datatypes.  It is used "as is" for dateTime; all other date/time datatypes except duration use the same model except that some of the six primary properties are required to have the value absent, instead of being required to have a numerical value.  (An ·optional· property, like ·timezoneOffset·, is always permitted to have the value absent.)

·timezoneOffset· values are limited to 14 hours, which is 840 (= 60 × 14) minutes.

Note: Leap-seconds are not permitted

Readers interested in when leap-seconds have been introduced should consult [USNO Historical List], which includes a list of times when the difference between TAI and