XML Schema Part 2: Datatypes

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XML Schema Part 2: Datatypes Second Edition

rec-20041028

W3C Recommendation

28 October 2004 http://www.w3.org/TR/2004/REC-xmlschema-2-20041028/ XML XHTML with visible change markup Independent copy of the schema for schema documents A schema for built-in datatypes only, in a separate namespace Independent copy of the DTD for schema documents http://www.w3.org/TR/xmlschema-2/ http://www.w3.org/TR/2004/PER-xmlschema-2-20040318/ Paul V. Biron Kaiser Permanente, for Health Level Seven Paul.V.Biron@kp.org Ashok Malhotra Microsoft (formerly of IBM) ashokma@microsoft.com

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 is a W3C Recommendation, which forms part of the Second Edition of XML Schema. This document has been reviewed by W3C Members and other interested parties and has been endorsed by the Director as a W3C Recommendation. It is a stable document and may be used as reference material or cited as a normative reference 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.

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 are discussed in the XML Schema Requirements document. The authors of this document are the members of the XML Schema Working Group. Different parts of this specification have different editors.

This version of this document incorporates some editorial changes from earlier versions.

This document was produced under the 24 January 2002 Current Patent Practice (CPP) as amended by the W3C Patent Policy Transition Procedure. The Working Group maintains a public list of patent disclosures relevant to this document; 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) with respect to this specification should disclose the information in accordance with section 6 of the W3C Patent Policy.

Please report errors in this document to www-xml-schema-comments@w3.org (archive). The list of known errors in this specification is available at http://www.w3.org/2001/05/xmlschema-errata.

The English version of this specification is the only normative version. Information about translations of this document is available at http://www.w3.org/2001/05/xmlschema-translations.

A list of current W3C Recommendations and other technical documents can be found at http://www.w3.org/TR.

This second edition is not a new version, it merely incorporates the changes dictated by the corrections to errors found in the first edition as agreed by the XML Schema Working Group, as a convenience to readers. A separate list of all such corrections is available at http://www.w3.org/2001/05/xmlschema-errata.

The errata list for this second edition is available at http://www.w3.org/2004/03/xmlschema-errata.

Please report errors in this document to www-xml-schema-comments@w3.org (archive).

Ashok Malhotra's affiliation has changed since the completion of editorial work on this second edition. He is now at Oracle, and can be contacted at <ashok.malhotra@oracle.com>.

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 1.0, provides a superset of the capabilities found in XML 1.0 document type definitions (DTDs) for specifying datatypes on elements and attributes.

English Extended Backus-Naur Form (formal grammar) 2001-04-03: pvb: added 0-9 to IsBlock production (to cover Latin1-Suppliment) 2001-04-03: pvb: fixed typos in \w (word char) multi-char escape: \p{S} -> \p{Z} and "control" -> "other" 2001-04-03: pvb: modified the pattern facet on language in the schema for datatypes to restrict sub-tags to no more than 8 chars, and changed the xsd:documentation to discuss section 2.12 of XML 1.02e and RFC 1766 instead of "production 33 of XML 1.0". 2001-04-03: pvb: fixed the order relation on duration from x <= y iff s+x <= s+y 2001-04-03: pvb: fixed incorrect values in duration partial order table (from <= and >= to <>. 2001-04-03: pvb: clarified a misleading statement in the lexical representation for durations regarding the omitition of "lower order items". 2001-04-03: pvb: clarified COS "maxInclusive-maxExclusive" and "minInclusive and minExclusive" to note that the prohibitions are within a single derivation step 2001-04-03: pvb: {typ,think}os in definition of restriction: missing "when" added and "one or more facet" changed to "zero or more" 2001-04-03: pvb: added gYearMonth and gDay to the list of types for which appendix E applies 2001-04-03: pvb: fixed incorrect comparisons in dateTime order relation algorithm (from <= to < and >= to >. 2001-04-03: pvb: in COS "maxExclusive-valid-restriction", fixed 2nd clause: {value} >= maxInclusive(parent) -> {value} > maxInclusive(parent) 2001-04-03: pvb: in COS "minExclusive-valid-restriction", fixed 1st clause: {value} > minExclusive(parent) -> {value} < minExclusive(parent) 2001-04-04: pvb: in COS "minExclusive-valid-restriction", fixed 3rd clause: {value} <= minInclusive(parent) -> {value} < minInclusive(parent) 2001-04-04: pvb: in COS "length-valid-restriction", fixed: {value} > length(parent) -> {value} != length(parent) 2001-04-04: pvb: changed antisymmetry to asymmetry in description of properties of partial orders: a R b and b R a ==> a = b -> a R b ==> not(b R a) 2001-04-04: pvb: fixed how cardinality gets valued for atomic types...if base is finite, then restriction is finite; else, added length, maxLength, totalDigits and fractionDigits to the list of facets which guarantee finite. 2001-04-10: pvb: fixed typo in schema def of ENTITIES; <xs:minLength value="1" id="ENTITES.minLength"/> went to <xs:minLength value="1" id="ENTITIES.minLength"/> 2001-04-12: pvb: added canonical form for hexBinary 2001-04-23: pvb: completed first pass at "refactoring": bringing all there is to know about any concept (e.g., a facet) into the same section, instead of having it spread all over the spec...thus, making this spec closer in organization to part 1. 2001-04-23: pvb: brought the stylesheet for parts 1 and 2 into alignment, so that both parts can use the same stylesheet. 2001-04-24: pvb: fixed several occurances of <xspecref> which should have been <xnt> (e.g., Name and NCName) 2001-04-24: pvb: fixed order in which derived types are listed in section 3 2001-04-25: pvb: removed dichot vs. tricot ednote 2001-04-25: pvb: clarified that optional + sign is not allowed in mantisa or exponent of canon rep for float/double 2001-04-25: pvb: clarified that both hh:mm are required for time zones 2001-04-25: pvb: fixed bug in dateTime normalization example 2001-04-25: pvb: fixed bug in indeterminate dateTime compare example 2001-04-25: pvb: updated reference to unicode char db 3.1, as well as the table of block names and general category values accordingly 2001-04-26: pvb: rewrote enumeration valid constraint to be less confusing 2001-04-26: pvb: corrected description of how cardinality gets valued to account for date types 2001-04-26: pvb: corrected signs of timezones in clauses C and D of dateTime comparison algorithm 2001-04-26: pvb: added note to ENTITY specifying value space is scoped, like the one in ENTITIES 2001-04-26: pvb: clarified that only the seconds part of durations may specify fractions 2001-04-26: pvb: corrected incorrect namespace name in section 3 2001-04-26: pvb: added "...(and other relevant portions of section 4)..." to the part of conformance that references the XML Rep of simple type defns. 2001-04-26: pvb: moved equal to section 4 2001-04-26: pvb: added fact that canonical rep for midnight is 00:00:00 to time 2001-04-26: pvb: added note to ordered and bounded that when inheriting value from basetype, the value for primitive types is in appx C. 2001-04-26: pvb: removed {pos,neg}CharGroupND productions from regex and redefined the charClassSub production as :== ( posCharGroup | negCharGroup) '-' charClassExpr (and moved a few other productions around as a result) 2003-03-05: pvb: errata: added "line feed (#xA)" to the list of chars excluded from the lexical space of normalizedString 2003-03-05: pvb: errata: corrected regex in 2e example in 2.5.1.2 and changed all mention of "whitespace" to "space" in descriptions of the lexical space of lists 2003-03-05: pvb: errata: removed mention of {total,fraction}Digits from description of lexical representation of decimal 2003-03-05: pvb: errata: changed {total,fraction}Digits validation rules to talk about "numbers expressible as ix10^-n",etc. instead of "number of digits = xxx".

Introduction Purpose

The 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 oriented	Document oriented
1999-01-21 1999-01-25 Ashok Malhotra 123 Microsoft Ave. Hawthorne NY 10532-0000 555-1234 555-4321 ]]>	Paul V. Biron Ashok Malhotra Latest draft We need to discuss the latest draft immediately. Either email me at mailto:paul.v.biron@kp.org or call 555-9876 ]]>

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.

Requirements

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

provide for primitive data typing, including byte, date, integer, sequence, SQL and Java primitive datatypes, etc.;

define a type system that is adequate for import/export from database systems (e.g., relational, object, OLAP);

distinguish requirements relating to lexical data representation vs. those governing an underlying information set;

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).

Scope

This portion of the XML Schema Language discusses 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 and .

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:

for compatibility

A feature of this specification included solely to ensure that schemas which use this feature remain compatible with

may

Conforming documents and processors are permitted to but need not behave as described.

match

(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 it belongs to the language generated by that production.

must

Conforming documents and processors are required to behave as described; otherwise they are in error.

error

A violation of the rules of this specification; results are undefined. Conforming software detect and report an error and recover from it.

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:

Constraint on Schemas

Constraints on the schema components themselves, i.e. conditions components satisfy to be components at all. Largely to be found in .

Schema Representation Constraint

Constraints on the representation of schema components in XML. Some but not all of these are expressed in and .

Validation Rule

Constraints expressed by schema components which information items satisfy to be schema-valid. Largely to be found in .

Type System

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

The datatypes discussed in this specification are computer representations of well known abstract concepts such as integer and date. It is not the place of this specification to define these abstract concepts; many other publications provide excellent definitions.

Datatype

In this specification, a datatype is a 3-tuple, consisting of a) a set of distinct values, called its , b) a set of lexical representations, called its , and c) a set of s that characterize properties of the , individual values or lexical items.

Value space

A value space is the set of values for a given datatype. Each value in the value space of a datatype is denoted by one or more literals in its .

The of a given datatype can be defined in one of the following ways:

defined axiomatically from fundamental notions (intensional definition) [see ]

enumerated outright (extensional definition) [see ]

defined by restricting the of an already defined datatype to a particular subset with a given set of properties [see ]

defined as a combination of values from one or more already defined (s) by a specific construction procedure [see and ]

s have certain properties. For example, they always have the property of , some definition of equality and might be , by which individual values within the can be compared to one another. The properties of s that are recognized by this specification are defined in .

Lexical space

In addition to its , each datatype also has a lexical space.

A lexical space is the set of valid literals for a datatype.

For example, "100" and "1.0E2" are two different literals from the of which both denote the same value. The type system defined in this specification provides a mechanism for schema designers to control the set of values and the corresponding set of acceptable literals of those values for a datatype.

The literals in the s defined in this specification have the following characteristics:

Interoperability:

The number of literals for each value has been kept small; for many datatypes there is a one-to-one mapping between literals and values. This makes it easy to exchange the values between different systems. In many cases, conversion from locale-dependent representations will be required on both the originator and the recipient side, both for computer processing and for interaction with humans.

Basic readability:

Textual, rather than binary, literals are used. This makes hand editing, debugging, and similar activities possible.

Ease of parsing and serializing:

Where possible, literals correspond to those found in common programming languages and libraries.

Canonical Lexical Representation

While the datatypes defined in this specification have, for the most part, a single lexical representation i.e. each value in the datatype's is denoted by a single literal in its , this is not always the case. The example in the previous section showed two literals for the datatype which denote the same value. Similarly, there be several literals for one of the date or time datatypes that denote the same value using different timezone indicators.

A canonical lexical representation is a set of literals from among the valid set of literals for a datatype such that there is a one-to-one mapping between literals in the canonical lexical representation and values in the .

Datatype dichotomies

It is useful to categorize the datatypes defined in this specification along various dimensions, forming a set of characterization dichotomies.

Atomic vs. list vs. union datatypes

The first distinction to be made is that between , and datatypes.

Atomic datatypes are those having values which are regarded by this specification as being indivisible.

List datatypes are those having values each of which consists of a finite-length (possibly empty) sequence of values of an datatype.

Union datatypes are those whose s and s are the union of the s and s of one or more other datatypes.

For example, a single token which es Nmtoken from could be the value of an datatype (); while a sequence of such tokens could be the value of a datatype ().

Atomic datatypes

datatypes can be either or . The of an datatype is a set of "atomic" values, which for the purposes of this specification, are not further decomposable. The of an datatype is a set of literals whose internal structure is specific to the datatype in question.

List datatypes

Several type systems (such as the one described in ) treat datatypes as special cases of the more general notions of aggregate or collection datatypes.

datatypes are always . The of a datatype is a set of finite-length sequences of values. The of a datatype is a set of literals whose internal structure is a white space-separated sequence of literals of the datatype of the items in the (where whitespace es S in ).

The or datatype that participates in the definition of a datatype is known as the itemType of that datatype.

]]> 8 10.5 12 ]]>

A datatype can be from an datatype whose allows whitespace (such as or )or a datatype any of whose 's allows whitespace. In such a case, regardless of the input, list items will be separated at whitespace boundaries.

]]> <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 of 3; rather, it is a of 18.

When a datatype is from a datatype, the following s apply:

For each of , and , the unit of length is measured in number of list items. The value of is fixed to the value collapse.

For datatypes the (and hence, the ) is composed of whitespace-separated literals of its . Hence, any specified when a new datatype is from a datatype is matched against each literal of the datatype and not against the literals of the datatype that serves as its .

123 456 123 987 456 123 987 567 456 ]]>

The for the datatype is defined as the lexical form in which each item in the has the canonical lexical representation of its .

Union datatypes

The and of a datatype are the union of the s and s of its . datatypes are always . Currently, there are no datatypes.

A prototypical example of a 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.

use="optional" use="optional" default="1" ]]>

Any number (greater than 1) of or s can participate in a type.

The datatypes that participate in the definition of a datatype are known as the memberTypes of that datatype.

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

For example, given the definition below, the first instance of the <size> element validates correctly as an , the second and third as .

]]> 1 large 1 ]]>

The for a datatype is defined as the lexical form in which the values have the canonical lexical representation of the appropriate .

A datatype which is in this specification need not be an "atomic" datatype in any programming language used to implement this specification. Likewise, a datatype which is a in this specification need not be a "list" datatype in any programming language used to implement this specification. Furthermore, a datatype which is a in this specification need not be a "union" datatype in any programming language used to implement this specification.

Primitive vs. derived datatypes

Next, we distinguish between and datatypes.

Primitive datatypes are those that are not defined in terms of other datatypes; they exist ab initio.

Derived datatypes are those that are defined in terms of other datatypes.

For example, in this specification, is a well-defined mathematical concept that cannot be defined in terms of other datatypes, while a is a special case of the more general datatype .

The simple ur-type definition is a special restriction of the ur-type definition whose name is anySimpleType in the XML Schema namespace. anySimpleType can be considered as the of all datatypes. anySimpleType is considered to have an unconstrained lexical space and a consisting of the union of the s of all the datatypes and the set of all lists of all members of the s of all the datatypes. There exists a conceptual datatype, whose name is anySimpleType, that is the simple version of the ur-type definition from . anySimpleType can be considered as the of all types. The of anySimpleType can be considered to be the of the s of all datatypes.

The datatypes defined by this specification fall into both the and categories. It is felt that a judiciously chosen set of datatypes will serve the widest possible audience by providing a set of convenient datatypes that can be used as is, as well as providing a rich enough base from which the variety of datatypes needed by schema designers can be .

In the example above, is from .

A datatype which is in this specification need not be a "primitive" datatype in any programming language used to implement this specification. Likewise, a datatype which is in this specification need not be a "derived" datatype in any programming language used to implement this specification.

As described in more detail in , each datatype be defined in terms of another datatype in one of three ways: 1) by assigning s which serve to restrict the of the datatype to a subset of that of the ; 2) by creating a datatype whose consists of finite-length sequences of values of its ; or 3) by creating a datatype whose consists of the union of the s of its .

Derived by restriction

A datatype is said to be by restriction from another datatype when values for zero or more s are specified that serve to constrain its and/or its to a subset of those of its .

Every datatype that is by restriction is defined in terms of an existing datatype, referred to as its base type. base types can be either or .

Derived by list

A datatype can be from another datatype (its ) by creating a that consists of a finite-length sequence of values of its .

Derived by union

One datatype can be from one or more datatypes by ing their s and, consequently, their s.

Built-in vs. user-derived datatypes

Built-in datatypes are those which are defined in this specification, and can be either or ;

User-derived datatypes are those datatypes that are defined by individual schema designers.

Conceptually there is no difference between the datatypes included in this specification and the datatypes which will be created by individual schema designers. The 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 datatypes in this specification serves to demonstrate the mechanics and utility of the datatype generation facilities of this specification.

A datatype which is in this specification need not be a "built-in" datatype in any programming language used to implement this specification. Likewise, a datatype which is in this specification need not be a "user-derived" datatype in any programming language used to implement this specification.

Built-in datatypes

Each built-in datatype in this specification (both and ) can be uniquely addressed via a URI Reference constructed as follows:

the base URI is the URI of the XML Schema namespace

the fragment identifier is the name of the datatype

For example, to address the 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:

the base URI is the URI of the XML Schema namespace

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:

the base URI is the URI of the XML Schema namespace

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

Namespace considerations

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

http://www.w3.org/2001/XMLSchema

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

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

This applies to both and datatypes.

Each datatype is also associated with a unique namespace. However, datatypes do not come from the namespace defined by this specification; rather, they come from the namespace of the schema in which they are defined (see XML Representation of Schemas in ).

Primitive datatypes

The datatypes defined by this specification are described below. For each datatype, the and are defined, s which apply to the datatype are listed and any datatypes from this datatype are specified.

datatypes can only be added by revisions to this specification.

string

The string datatype represents character strings in XML. The of string is the set of finite-length sequences of characters (as defined in ) that the Char production from . 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 code point, which is an integer.

Many human languages have writing systems that require child elements for control of aspects such as bidirectional formating or ruby annotation (see and Section 8.2.4 Overriding the bidirectional algorithm: the BDO element of ). 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 .

As noted in , the fact that this specification does not specify an for does not preclude other applications from treating strings as being ordered.

Derived datatypes boolean

boolean has the required to support the mathematical concept of binary-valued logic: {true, false}.

Lexical representation

An instance of a datatype that is defined as can have the following legal literals {true, false, 1, 0}.

Canonical representation

The canonical representation for boolean is the set of literals {true, false}.

decimal

decimal represents a subset of the real numbers, which can be represented by decimal numeralsarbitrary precision decimal numbers. The of decimal is the set of numbers that can be obtained by multiplying an integer by a non-positive power of ten, i.e., expressible as i × 10^-n where i and n are integers and n >= 0the values i × 10^-n, where i and n are integers such that n >= 0. Precision is not reflected in this value space; the number 2.0 is not distinct from the number 2.00. The on decimal is the order relation on real numbers, restricted to this subset: x < y iff y - x is positive.

The of types derived from decimal with a value for of p is the set of values i × 10^-n, where n and i are integers such that p >= n >= 0 and the number of significant decimal digits in i is less than or equal to p.

The of types derived from decimal with a value for of s is the set of values i × 10^-n, where i and n are integers such that 0 <= n <= s.

All processors support decimal numbers with a minimum of 18 decimal digits (i.e., with a of 18). However, processors set an application-defined limit on the maximum number of decimal digits they are prepared to support, in which case that application-defined maximum number be clearly documented.

Lexical representation

decimal has a lexical representation consisting of a finite-length sequence of decimal digits (#x30-#x39) separated by a period as a decimal indicator. If is specified, the number of digits must be less than or equal to . If is specified, the number of digits following the decimal point must be less than or equal to the . 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.

Canonical representation

The canonical representation for decimal is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited. The decimal point is required. 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.

Derived datatypes float

float is patterned aftercorresponds to the IEEE single-precision 32-bit floating point type . The basic of float consists of the values m × 2^e, where m is an integer whose absolute value is less than 2^24, and e is an integer between -149 and 104, inclusive. In addition to the basic described above, the of float also contains the following three special values: positive and negative zero, positive and negative infinity and not-a-number (NaN). The on float is: x < y iff y - x is positive for x and y in the value space. Positive infinity is greater than all other non-NaN values. NaN equals itself but is with (neither greater than nor less than) any other value in the . Positive zero is greater than negative zero. Not-a-number equals itself and is greater than all float values including positive infinity.

"Equality" in this Recommendation is defined to be "identity" (i.e., values that are identical in the are equal and vice versa). Identity must be used for the few operations that are defined in this Recommendation. Applications using any of the datatypes defined in this Recommendation may use different definitions of equality for computational purposes; -based computation systems are examples. Nothing in this Recommendation should be construed as requiring that such applications use identity as their equality relationship when computing.

Any value with the value used for the four bounding facets (, , , and ) will be excluded from the resulting restricted . In particular, when "NaN" is used as a facet value for a bounding facet, since no other float values are with it, the result is a either having NaN as its only member (the inclusive cases) or that is empty (the exclusive cases). If any other value is used for a bounding facet, NaN will be excluded from the resulting restricted ; to add NaN back in requires union with the NaN-only space.

This datatype differs from that of in that there is only one NaN and only one zero. This makes the equality and ordering of values in the data space differ from that of only in that for schema purposes NaN = NaN.

A literal in the representing a decimal number d maps to the normalized value in the of float that is closest to d in the sense defined by ; if d is exactly halfway between two such values then the even value is chosen.

Lexical representation

float values have a lexical representation consisting of a mantissa followed, optionally, by the character "E" or "e", followed by an exponent. The exponent be an . The mantissa must be a number. The representations for exponent and mantissa must follow the lexical rules for and . If the "E" or "e" and the following exponent are omitted, an exponent value of 0 is assumed.

The special values positive and negative zero, positive and negative infinity and not-a-number have lexical representations 0, -0, INF, -INF and NaN, respectively. Lexical representations for zero may take a positive or negative sign.

For example, -1E4, 1267.43233E12, 12.78e-2, 12 , -0, 0 and INF are all legal literals for float.

Canonical representation

The canonical representation for float is defined by prohibiting certain options from the . Specifically, the exponent must be indicated by "E". Leading zeroes and the preceding optional "+" sign are prohibited in the exponent. If the exponent is zero, it must be indicated by "E0". For the mantissa, the preceding optional "+" sign is prohibited and the decimal point is required. For the exponent, the preceding optional "+" sign is prohibited. Leading and trailing zeroes are prohibited subject to the following: number representations must be normalized such that there is a single digit which is non-zero to the left of the decimal point and at least a single digit to the right of the decimal point unless the value being represented is zero. The canonical representation for zero is 0.0E0.

double

The double datatype is patterned after the corresponds to IEEE double-precision 64-bit floating point type . The basic of double consists of the values m × 2^e, where m is an integer whose absolute value is less than 2^53, and e is an integer between -1075 and 970, inclusive. In addition to the basic described above, the of double also contains the following three special values: positive and negative zero, positive and negative infinity and not-a-number (NaN). The on double is: x < y iff y - x is positive for x and y in the value space. Positive infinity is greater than all other non-NaN values. NaN equals itself but is with (neither greater than nor less than) any other value in the . Positive zero is greater than negative zero. Not-a-number equals itself and is greater than all float values including positive infinity.

Any value with the value used for the four bounding facets (, , , and ) will be excluded from the resulting restricted . In particular, when "NaN" is used as a facet value for a bounding facet, since no other double values are with it, the result is a either having NaN as its only member (the inclusive cases) or that is empty (the exclusive cases). If any other value is used for a bounding facet, NaN will be excluded from the resulting restricted ; to add NaN back in requires union with the NaN-only space.

A literal in the representing a decimal number d maps to the normalized value in the of double that is closest to d; if d is exactly halfway between two such values then the even value is chosen. This is the best approximation of d (, ), which is more accurate than the mapping required by .

Lexical representation

double values have a lexical representation consisting of a mantissa followed, optionally, by the character "E" or "e", followed by an exponent. The exponent be an integer. The mantissa must be a decimal number. The representations for exponent and mantissa must follow the lexical rules for and . If the "E" or "e" and the following exponent are omitted, an exponent value of 0 is assumed.

For example, -1E4, 1267.43233E12, 12.78e-2, 12 , -0, 0 and INF are all legal literals for double.

Canonical representation

The canonical representation for double is defined by prohibiting certain options from the . Specifically, the exponent must be indicated by "E". Leading zeroes and the preceding optional "+" sign are prohibited in the exponent. If the exponent is zero, it must be indicated by "E0". For the mantissa, the preceding optional "+" sign is prohibited and the decimal point is required. For the exponent, the preceding optional "+" sign is prohibited. Leading and trailing zeroes are prohibited subject to the following: number representations must be normalized such that there is a single digit which is non-zero to the left of the decimal point and at least a single digit to the right of the decimal point unless the value being represented is zero. The canonical representation for zero is 0.0E0.

duration

duration represents a duration of time. The of duration is a six-dimensional space where the coordinates designate the Gregorian year, month, day, hour, minute, and second components defined in § 5.5.3.2 of , respectively. These components are ordered in their significance by their order of appearance i.e. as year, month, day, hour, minute, and second.

All processors support year values with a minimum of 4 digits (i.e., YYYY) and a minimum fractional second precision of milliseconds or three decimal digits (i.e. s.sss). However, processors set an application-defined limit on the maximum number of digits they are prepared to support in these two cases, in which case that application-defined maximum number be clearly documented.

Lexical representation

The lexical representation for duration is the extended format PnYn MnDTnH nMnS, where nY represents the number of years, nM the number of months, nD the number of days, 'T' is the date/time separator, nH the number of hours, nM the number of minutes and nS the number of seconds. The number of seconds can include decimal digits to arbitrary precision.

The values of the Year, Month, Day, Hour and Minutes components are not restricted but allow an arbitrary unsigned integer, i.e., an integer that conforms to the pattern [0-9]+.. Similarly, the value of the Seconds component allows an arbitrary unsigned decimal. Following , at least one digit must follow the decimal point if it appears. That is, the value of the Seconds component must conform to the pattern [0-9]+(\.[0-9]+)?. Thus, the lexical representation of duration does not follow the alternative format of § 5.5.3.2.1 of .

An optional preceding minus sign ('-') is allowed, to indicate a negative duration. If the sign is omitted a positive duration is indicated. See also .

For example, to indicate a duration of 1 year, 2 months, 3 days, 10 hours, and 30 minutes, one would write: P1Y2M3DT10H30M. One could also indicate a duration of minus 120 days as: -P120D.

Reduced precision and truncated representations of this format are allowed provided they conform to the following:

If the number of years, months, days, hours, minutes, or seconds in any expression equals zero, the number and its corresponding designator be omitted. However, at least one number and its designator be present.

The seconds part have a decimal fraction.

The designator 'T' mustshall be absent if and only if all of the time items are absent. The designator 'P' must always be present.

For example, P1347Y, P1347M and P1Y2MT2H are all allowed; P0Y1347M and P0Y1347M0D are allowed. P-1347M is not allowed although -P1347M is allowed. P1Y2MT is not allowed.

Order relation on duration

In general, the on duration is a partial order since there is no determinate relationship between certain durations such as one month (P1M) and 30 days (P30D). The of two duration values x and y is x < y iff s+x < s+y for each qualified s in the list below. These values for s cause the greatest deviations in the addition of dateTimes and durations. Addition of durations to time instants is defined in .

1696-09-01T00:00:00Z

1697-02-01T00:00:00Z

1903-03-01T00:00:00Z

1903-07-01T00:00:00Z

The following table shows the strongest relationship that can be determined between example durations. The symbol <> means that the order relation is indeterminate. Note that because of leap-seconds, a seconds field can vary from 59 to 60. However, because of the way that addition is defined in , they are still totally ordered.

	Relation
P1Y	> P364D	<> P365D				<> P366D	< P367D
P1M	> P27D	<> P28D	<> P29D		<> P30D	<> P31D	< P32D
P5M	> P149D	<> P150D	<> P151D	<> P152D		<> P153D	< P154D

Implementations are free to optimize the computation of the ordering relationship. For example, the following table can be used to compare durations of a small number of months against days.

	Months	1	2	3	4	5	6	7	8	9	10	11	12	13	...
Days	Minimum	28	59	89	120	150	181	212	242	273	303	334	365	393	...
Days	Maximum	31	62	92	123	153	184	215	245	276	306	337	366	397	...

Totally ordered durations

Certain derived datatypes of durations can be guaranteed have a total order. For this, they must have fields from only one row in the list below and the time zone must either be required or prohibited.

year, month

day, hour, minute, second

For example, a datatype could be defined to correspond to the datatype Year-Month interval that required a four digit year field and a two digit month field but required all other fields to be unspecified. This datatype could be defined as below and would have a total order.

]]> dateTime

dateTime values may be viewed as objects with integer-valued year, month, day, hour and minute properties, a decimal-valued second property, and a boolean timezoned property. Each such object also has one decimal-valued method or computed property, timeOnTimeline, whose value is always a decimal number; the values are dimensioned in seconds, the integer 0 is 0001-01-01T00:00:00 and the value of timeOnTimeline for other dateTime values is computed using the Gregorian algorithm as modified for leap-seconds. The timeOnTimeline values form two related "timelines", one for timezoned values and one for non-timezoned values. Each timeline is a copy of the of , with integers given units of seconds.

The of dateTime is closely related to the dates and times described in ISO 8601. For clarity, the text above specifies a particular origin point for the timeline. It should be noted, however, that schema processors need not expose the timeOnTimeline value to schema users, and there is no requirement that a timeline-based implementation use the particular origin described here in its internal representation. Other interpretations of the which lead to the same results (i.e., are isomorphic) are of course acceptable.

All timezoned times are Coordinated Universal Time (UTC, sometimes called "Greenwich Mean Time"). Other timezones indicated in lexical representations are converted to UTC during conversion of literals to values. "Local" or untimezoned times are presumed to be the time in the timezone of some unspecified locality as prescribed by the appropriate legal authority; currently there are no legally prescribed timezones which are durations whose magnitude is greater than 14 hours. The value of each numeric-valued property (other than timeOnTimeline) is limited to the maximum value within the interval determined by the next-higher property. For example, the day value can never be 32, and cannot even be 29 for month 02 and year 2002 (February 2002).

The date and time datatypes described in this recommendation were inspired by . '0001' is the lexical representation of the year 1 of the Common Era (1 CE, sometimes written "AD 1" or "1 AD"). There is no year 0, and '0000' is not a valid lexical representation. '-0001' is the lexical representation of the year 1 Before Common Era (1 BCE, sometimes written "1 BC").

Those using this (1.0) version of this Recommendation to represent negative years should be aware that the interpretation of lexical representations beginning with a '-' is likely to change in subsequent versions.

makes no mention of the year 0; in the form '0000' was disallowed and this recommendation disallows it as well. However, , which became available just as we were completing version 1.0, allows the form '0000', representing the year 1 BCE. A number of external commentators have also suggested that '0000' be allowed, as the lexical representation for 1 BCE, which is the normal usage in astronomical contexts. It is the intention of the XML Schema Working Group to allow '0000' as a lexical representation in the dateTime, date, gYear, and gYearMonth datatypes in a subsequent version of this Recommendation. '0000' will be the lexical representation of 1 BCE (which is a leap year), '-0001' will become the lexical representation of 2 BCE (not 1 BCE as in this (1.0) version), '-0002' of 3 BCE, etc.

See the conformance note in which applies to this datatype as well.

Lexical representation

The of dateTime consists of finite-length sequences of characters of the form: '-'? yyyy '-' mm '-' dd 'T' hh ':' mm ':' ss ('.' s+)? (zzzzzz)?, where

'-'? yyyy is a four-or-more digit optionally negative-signed numeral that represents the year; if more than four digits, leading zeros are prohibited, and '0000' is prohibited (see the Note above ; also note that a plus sign is not permitted);

the remaining '-'s are separators between parts of the date portion;

the first mm is a two-digit numeral that represents the month;

dd is a two-digit numeral that represents the day;

'T' is a separator indicating that time-of-day follows;

hh is a two-digit numeral that represents the hour; '24' is permitted if the minutes and seconds represented are zero, and the dateTime value so represented is the first instant of the following day (the hour property of a dateTime object in the cannot have a value greater than 23);

':' is a separator between parts of the time-of-day portion;

the second mm is a two-digit numeral that represents the minute;

ss is a two-integer-digit numeral that represents the whole seconds;

'.' s+ (if present) represents the fractional seconds;

zzzzzz (if present) represents the timezone (as described below).

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 2002-10-10T17:00:00Z, five hours later than 2002-10-10T12:00:00Z.

For further guidance on arithmetic with dateTimes and durations, see .

Canonical representation

Except for trailing fractional zero digits in the seconds representation, '24:00:00' time representations, and timezone (for timezoned values), the mapping from literals to values is one-to-one. Where there is more than one possible representation, the canonical representation is as follows:

The 2-digit numeral representing the hour must not be '24';

The fractional second string, if present, must not end in '0';

for timezoned values, the timezone must be represented with 'Z' (All timezoned dateTime values are UTC.).

Timezones

Timezones are durations with (integer-valued) hour and minute properties (with the hour magnitude limited to at most 14, and the minute magnitude limited to at most 59, except that if the hour magnitude is 14, the minute value must be 0); they may be both positive or both negative.

The lexical representation of a timezone is a string of the form: (('+' | '-') hh ':' mm) | 'Z', where

hh is a two-digit numeral (with leading zeros as required) that represents the hours,

mm is a two-digit numeral that represents the minutes,

'+' indicates a nonnegative duration,

'-' indicates a nonpositive duration.

The mapping so defined is one-to-one, except that '+00:00', '-00:00', and 'Z' all represent the same zero-length duration timezone, UTC; 'Z' is its canonical representation.

When a timezone is added to a UTC dateTime, the result is the date and time "in that timezone". For example, 2002-10-10T12:00:00+05:00 is 2002-10-10T07:00:00Z and 2002-10-10T00:00:00+05:00 is 2002-10-09T19:00:00Z.

Order relation on dateTime

dateTime value objects on either timeline are totally ordered by their timeOnTimeline values; between the two timelines, dateTime value objects are ordered by their timeOnTimeline values when their timeOnTimeline values differ by more than fourteen hours, with those whose difference is a duration of 14 hours or less being .

In general, the on dateTime is a partial order since there is no determinate relationship between certain instants. For example, there is no determinate ordering between (a) 2000-01-20T12:00:00 and (b) 2000-01-20T12:00:00Z. Based on timezones currently in use, (c) could vary from 2000-01-20T12:00:00+12:00 to 2000-01-20T12:00:00-13:00. It is, however, possible for this range to expand or contract in the future, based on local laws. Because of this, the following definition uses a somewhat broader range of indeterminate values: +14:00..-14:00.

The following definition uses the notation S[year] to represent the year field of S, S[month] to represent the month field, and so on. The notation (Q & "-14:00") means adding the timezone -14:00 to Q, where Q did not already have a timezone. This is a logical explanation of the process. Actual implementations are free to optimize as long as they produce the same results.

The ordering between two dateTimes P and Q is defined by the following algorithm:

A.Normalize P and Q. That is, if there is a timezone present, but it is not Z, convert it to Z using the addition operation defined in

Thus 2000-03-04T23:00:00+03:00 normalizes to 2000-03-04T20:00:00Z

B. If P and Q either both have a time zone or both do not have a time zone, compare P and Q field by field from the year field down to the second field, and return a result as soon as it can be determined. That is:

For each i in {year, month, day, hour, minute, second}

If P[i] and Q[i] are both not specified, continue to the next i

If P[i] is not specified and Q[i] is, or vice versa, stop and return P <> Q

If P[i] < Q[i], stop and return P < Q

If P[i] > Q[i], stop and return P > Q

Stop and return P = Q

C.Otherwise, if P contains a time zone and Q does not, compare as follows:

P < Q if P < (Q with time zone +14:00)

P > Q if P > (Q with time zone -14:00)

P <> Q otherwise, that is, if (Q with time zone +14:00) < P < (Q with time zone -14:00)

D. Otherwise, if P does not contain a time zone and Q does, compare as follows:

P < Q if (P with time zone -14:00) < Q.

P > Q if (P with time zone +14:00) > Q.

P <> Q otherwise, that is, if (P with time zone +14:00) < Q < (P with time zone -14:00)

Examples:

Determinate	Indeterminate
2000-01-15T00:00:00 < 2000-02-15T00:00:00	2000-01-01T12:00:00 <> 1999-12-31T23:00:00Z
2000-01-15T12:00:00 < 2000-01-16T12:00:00Z	2000-01-16T12:00:00 <> 2000-01-16T12:00:00Z
	2000-01-16T00:00:00 <> 2000-01-16T12:00:00Z

Totally ordered dateTimes

Certain derived types from dateTime can be guaranteed have a total order. To do so, they must require that a specific set of fields are always specified, and that remaining fields (if any) are always unspecified. For example, the date datatype without time zone is defined to contain exactly year, month, and day. Thus dates without time zone have a total order among themselves.

time

time represents an instant of time that recurs every day. The of time is the space of time of day values as defined in § 5.3 of . Specifically, it is a set of zero-duration daily time instances.

Since the lexical representation allows an optional time zone indicator, time values are partially ordered because it may not be able to determine the order of two values one of which has a time zone and the other does not. The order relation on time values is the using an arbitrary date. See also . Pairs of time values with or without time zone indicators are totally ordered.

See the conformance note in which applies to the seconds part of this datatype as well.

Lexical representation

The lexical representation for time is the left truncated lexical representation for : hh:mm:ss.sss with optional following time zone indicator. For example, to indicate 1:20 pm for Eastern Standard Time which is 5 hours behind Coordinated Universal Time (UTC), one would write: 13:20:00-05:00. See also .

Canonical representation

The canonical representation for time is defined by prohibiting certain options from the . Specifically, either the time zone must be omitted or, if present, the time zone must be Coordinated Universal Time (UTC) indicated by a "Z". Additionally, the canonical representation for midnight is 00:00:00.

date

The of date consists of top-open intervals of exactly one day in length on the timelines of , beginning on the beginning moment of each day (in each timezone), i.e. '00:00:00', up to but not including '24:00:00' (which is identical with '00:00:00' of the next day). For nontimezoned values, the top-open intervals disjointly cover the nontimezoned timeline, one per day. For timezoned values, the intervals begin at every minute and therefore overlap.

A "date object" is an object with year, month, and day properties just like those of objects, plus an optional timezone-valued timezone property. (As with values of timezones are a special case of durations.) Just as a object corresponds to a point on one of the timelines, a date object corresponds to an interval on one of the two timelines as just described.

Timezoned date values track the starting moment of their day, as determined by their timezone; said timezone is generally recoverable for canonical representations. The recoverable timezone is that duration which is the result of subtracting the first moment (or any moment) of the timezoned date from the first moment (or the corresponding moment) UTC on the same date. s are always durations between '+12:00' and '-11:59'. This "timezone normalization" (which follows automatically from the definition of the date ) is explained more in .

For example: the first moment of 2002-10-10+13:00 is 2002-10-10T00:00:00+13, which is 2002-10-09T11:00:00Z, which is also the first moment of 2002-10-09-11:00. Therefore 2002-10-10+13:00 is 2002-10-09-11:00; they are the same interval.

For most timezones, either the first moment or last moment of the day (a value, always UTC) will have a date portion different from that of the date itself! However, noon of that date (the midpoint of the interval) in that (normalized) timezone will always have the same date portion as the date itself, even when that noon point in time is normalized to UTC. For example, 2002-10-10-05:00 begins during 2002-10-09Z and 2002-10-10+05:00 ends during 2002-10-11Z, but noon of both 2002-10-10-05:00 and 2002-10-10+05:00 falls in the interval which is 2002-10-10Z.

See the conformance note in which applies to the year part of this datatype as well.

Lexical representation

For the following discussion, let the "date portion" of a or date object be an object similar to a or date object, with similar year, month, and day properties, but no others, having the same value for these properties as the original or date object.

The of date consists of finite-length sequences of characters of the form: '-'? yyyy '-' mm '-' dd zzzzzz? where the date and optional timezone are represented exactly the same way as they are for . The first moment of the interval is that represented by: '-' yyyy '-' mm '-' dd 'T00:00:00' zzzzzz? and the least upper bound of the interval is the timeline point represented (noncanonically) by: '-' yyyy '-' mm '-' dd 'T24:00:00' zzzzzz?.

The of a date will always be a duration between '+12:00' and '11:59'. Timezone lexical representations, as explained for , can range from '+14:00' to '-14:00'. The result is that literals of dates with very large or very negative timezones will map to a "normalized" date value with a different from that represented in the original representation, and a matching difference of +/- 1 day in the date itself.

Canonical representation

Given a member of the date , the date portion of the canonical representation (the entire representation for nontimezoned values, and all but the timezone representation for timezoned values) is always the date portion of the canonical representation of the interval midpoint (the representation, truncated on the right to eliminate 'T' and all following characters). For timezoned values, append the canonical representation of the .

gYearMonth

gYearMonth represents a specific gregorian month in a specific gregorian year. The of gYearMonth is the set of Gregorian calendar months as defined in § 5.2.1 of . Specifically, it is a set of one-month long, non-periodic instances e.g. 1999-10 to represent the whole month of 1999-10, independent of how many days this month has.

Since the lexical representation allows an optional time zone indicator, gYearMonth values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gYearMonth values are considered as periods of time, the order relation on gYearMonth values is the order relation on their starting instants. This is discussed in . See also . Pairs of gYearMonth values with or without time zone indicators are totally ordered.

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.

See the conformance note in which applies to the year part of this datatype as well.

Lexical representation

The lexical representation for gYearMonth is the reduced (right truncated) lexical representation for : CCYY-MM. No left truncation is allowed. An optional following time zone qualifier is allowed. To accommodate year values outside the range from 0001 to 9999, additional digits can be added to the left of this representation and a preceding "-" sign is allowed.

For example, to indicate the month of May 1999, one would write: 1999-05. See also .

gYear

gYear represents a gregorian calendar year. The of gYear is the set of Gregorian calendar years as defined in § 5.2.1 of . Specifically, it is a set of one-year long, non-periodic instances e.g. lexical 1999 to represent the whole year 1999, independent of how many months and days this year has.

Since the lexical representation allows an optional time zone indicator, gYear values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gYear values are considered as periods of time, the order relation on gYear values is the order relation on their starting instants. This is discussed in . See also . Pairs of gYear values with or without time zone indicators are totally ordered.

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.

See the conformance note in which applies to the year part of this datatype as well.

Lexical representation

The lexical representation for gYear is the reduced (right truncated) lexical representation for : CCYY. No left truncation is allowed. An optional following time zone qualifier is allowed as for . To accommodate year values outside the range from 0001 to 9999, additional digits can be added to the left of this representation and a preceding "-" sign is allowed.

For example, to indicate 1999, one would write: 1999. See also .

gMonthDay

gMonthDay is a gregorian date that recurs, specifically a day of the year such as the third of May. Arbitrary recurring dates are not supported by this datatype. The of gMonthDay is the set of calendar dates, as defined in § 3 of . Specifically, it is a set of one-day long, annually periodic instances.

Since the lexical representation allows an optional time zone indicator, gMonthDay values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gMonthDay values are considered as periods of time, in an arbitrary leap year, the order relation on gMonthDay values is the order relation on their starting instants. This is discussed in . See also . Pairs of gMonthDay values with or without time zone indicators are totally ordered.

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.

Lexical representation

The lexical representation for gMonthDay is the left truncated lexical representation for : --MM-DD. An optional following time zone qualifier is allowed as for . No preceding sign is allowed. No other formats are allowed. See also .

This datatype can be used to represent a specific day in a month. To say, for example, that my birthday occurs on the 14th of September ever year.

gDay

gDay is a gregorian day that recurs, specifically a day of the month such as the 5th of the month. Arbitrary recurring days are not supported by this datatype. The of gDay is the space of a set of calendar dates as defined in § 3 of . Specifically, it is a set of one-day long, monthly periodic instances.

This datatype can be used to represent a specific day of the month. To say, for example, that I get my paycheck on the 15th of each month.

Since the lexical representation allows an optional time zone indicator, gDay values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gDay values are considered as periods of time, in an arbitrary month that has 31 days, the order relation on gDay values is the order relation on their starting instants. This is discussed in . See also . Pairs of gDay values with or without time zone indicators are totally ordered.

Because days in one calendar only rarely correspond to days 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.

Lexical representation

The lexical representation for gDay is the left truncated lexical representation for : ---DD . An optional following time zone qualifier is allowed as for . No preceding sign is allowed. No other formats are allowed. See also .

gMonth

gMonth is a gregorian month that recurs every year. The of gMonth is the space of a set of calendar months as defined in § 3 of . Specifically, it is a set of one-month long, yearly periodic instances.

This datatype can be used to represent a specific month. To say, for example, that Thanksgiving falls in the month of November.

Since the lexical representation allows an optional time zone indicator, gMonth values are partially ordered because it may not be possible to unequivocally determine the order of two values one of which has a time zone and the other does not. If gMonth values are considered as periods of time, the order relation on gMonth is the order relation on their starting instants. This is discussed in . See also . Pairs of gMonth values with or without time zone indicators are totally ordered.

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.

Lexical representation

The lexical representation for gMonth is the left and right truncated lexical representation for : --MM--. An optional following time zone qualifier is allowed as for . No preceding sign is allowed. No other formats are allowed. See also .

hexBinary

hexBinary represents arbitrary hex-encoded binary data. The of hexBinary is the set of finite-length sequences of binary octets.

Lexical Representation

hexBinary has a lexical representation where each binary octet is encoded as a character tuple, consisting of two hexadecimal digits ([0-9a-fA-F]) representing the octet code. For example, "0FB7" is a hex encoding for the 16-bit integer 4023 (whose binary representation is 111110110111).

Canonical RepresentationRrepresentation

The canonical representation for hexBinary is defined by prohibiting certain options from the . Specifically, the lower case hexadecimal digits ([a-f]) are not allowed.

base64Binary

base64Binary represents Base64-encoded arbitrary binary data. The of base64Binary is the set of finite-length sequences of binary octets. For base64Binary data the entire binary stream is encoded using the Base64 Content-Transfer-Encoding defined in Section 6.8 of Alphabet in .

The lexical forms of base64Binary values are limited to the 65 characters of the Base64 Alphabet defined in , i.e., a-z, A-Z, 0-9, the plus sign (+), the forward slash (/) and the equal sign (=), together with the characters defined in as white space. No other characters are allowed.

For compatibility with older mail gateways, suggests that base64 data should have lines limited to at most 76 characters in length. This line-length limitation is not mandated in the lexical forms of base64Binary data and must not be enforced by XML Schema processors.

The lexical space of base64Binary is given by the following grammar (the notation is that used in ); legal lexical forms must match the Base64Binary production.

Base64Binary ::= ((B64S B64S B64S B64S)* ((B64S B64S B64S B64) | (B64S B64S B16S '=') | (B64S B04S '=' #x20? '=')))? B64S ::= B64 #x20? B16S ::= B16 #x20? B04S ::= B04 #x20? B04 ::= [AQgw] B16 ::= [AEIMQUYcgkosw048] B64 ::= [A-Za-z0-9+/]

Note that this grammar requires the number of non-whitespace characters in the lexical form to be a multiple of four, and for equals signs to appear only at the end of the lexical form; strings which do not meet these constraints are not legal lexical forms of base64Binary because they cannot successfully be decoded by base64 decoders.

The above definition of the lexical space is more restrictive than that given in as regards whitespace -- this is not an issue in practice. Any string compatible with the RFC can occur in an element or attribute validated by this type, because the 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 canonical lexical form of a base64Binary data value is the base64 encoding of the value which matches the Canonical-base64Binary production in the following grammar:

Canonical-base64Binary ::= (B64 B64 B64 B64)* ((B64 B64 B16 '=') | (B64 B04 '=='))?

For some values the canonical form defined above does not conform to , which requires breaking with linefeeds at appropriate intervals.

The length of a base64Binary value is the number of octets it contains. This may be calculated from the lexical form 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: explicitly references 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

anyURI

anyURI represents a Uniform Resource Identifier Reference (URI). An anyURI value can be absolute or relative, and may have an optional fragment identifier (i.e., it may be a URI Reference). This type should be used to specify the intention that the value fulfills the role of a URI as defined by , as amended by .

The mapping from anyURI values to URIs is as defined by the URI reference escaping procedure defined in Section 5.4 Locator Attribute of (see also Section 8 Character Encoding in URI References of ). 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 , as amended by , where appropriate to identify resources.

Section 5.4 Locator Attribute of requires that relative URI references be absolutized as defined in before use. This is an XLink-specific requirement and is not appropriate for XML Schema, since neither the nor the of the type are restricted to absolute URIs. Accordingly absolutization must not be performed by schema processors as part of schema validation.

Each URI scheme imposes specialized syntax rules for URIs in that scheme, including restrictions on the syntax of allowed fragmentfragement identifiers. Because it is impractical for processors to check that a value is a context-appropriate URI reference, this specification follows the lead of (as amended by ) in this matter: such rules and restrictions are not part of type validity and are not checked by processors. Thus in practice the above definition imposes only very modest obligations on processors.

Lexical representation

The of anyURI is finite-length character sequences which, when the algorithm defined in Section 5.4 of is applied to them, result in strings which are legal URIs according to , as amended by .

Spaces are, in principle, allowed in the of anyURI, however, their use is highly discouraged (unless they are encoded by %20).

QName

QName represents XML qualified names. The of QName is the set of tuples {namespace name, local part}, where namespace name is an and local part is an . The of QName is the set of strings that the QName production of .

The mapping between literals in the and values in the of QName requires a namespace declaration to be in scope for the context in which QName is used.

NOTATION

NOTATION represents the NOTATION attribute type from . The of NOTATION is the set of s of notations declared in the current schema. The of NOTATION is the set of all names of notations declared in the current schema (in the form of s).

enumeration facet value required for NOTATION

It is an for NOTATION to be used directly in a schema. Only datatypes that are from NOTATION by specifying a value for can be used in a schema.

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

Derived datatypes

This section gives conceptual definitions for all datatypes defined by this specification. The XML representation used to define datatypes (whether or ) is given in section and the complete definitions of the datatypes are provided in Appendix A .

normalizedString

normalizedString represents white space normalized strings. The of normalizedString is the set of strings that do not contain the carriage return (#xD), line feed (#xA) nor tab (#x9) characters. The of normalizedString is the set of strings that do not contain the carriage return (#xD), line feed (#xA) nor tab (#x9) characters. The of normalizedString is .

Derived datatypes token

token represents tokenized strings. The 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 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 of token is .

Derived datatypes language

language represents natural language identifiers as defined by by . The of language is the set of all strings that are valid language identifiers as defined in the language identification section of . The of language is the set of all strings that conform to the pattern [a-zA-Z]{1,8}(-[a-zA-Z0-9]{1,8})* are valid language identifiers as defined in the language identification section of . The of language is .

NMTOKEN

NMTOKEN represents the NMTOKEN attribute type from . The of NMTOKEN is the set of tokens that the Nmtoken production in . The of NMTOKEN is the set of strings that the Nmtoken production in . The of NMTOKEN is .

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

Derived datatypes NMTOKENS

NMTOKENS represents the NMTOKENS attribute type from . The of NMTOKENS is the set of finite, non-zero-length sequences of s. The of NMTOKENS is the set of white space-separated lists of tokens, of which each token is in the of . The of NMTOKENS is .

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

Name

Name represents XML Names. The of Name is the set of all strings which the Name production of . The of Name is the set of all strings which the Name production of . The of Name is .

Derived datatypes NCName

NCName represents XML "non-colonized" Names. The of NCName is the set of all strings which the NCName production of . The of NCName is the set of all strings which the NCName production of . The of NCName is .

Derived datatypes ID

ID represents the ID attribute type from . The of ID is the set of all strings that the NCName production in . The of ID is the set of all strings that the NCName production in . The of ID is .

For compatibility (see ) ID should be used only on attributes.

IDREF

IDREF represents the IDREF attribute type from . The of IDREF is the set of all strings that the NCName production in . The of IDREF is the set of strings that the NCName production in . The of IDREF is .

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

Derived datatypes IDREFS

IDREFS represents the IDREFS attribute type from . The of IDREFS is the set of finite, non-zero-length sequences of s. The of IDREFS is the set of white space-separated lists of tokens, of which each token is in the of . The of IDREFS is .

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

ENTITY

ENTITY represents the ENTITY attribute type from . The of ENTITY is the set of all strings that the NCName production in and have been declared as an unparsed entity in a document type definition. The of ENTITY is the set of all strings that the NCName production in . The of ENTITY is .

The of ENTITY is scoped to a specific instance document.

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

Derived datatypes ENTITIES

ENTITIES represents the ENTITIES attribute type from . The of ENTITIES is the set of finite, non-zero-length sequences of s that have been declared as unparsed entities in a document type definition. The of ENTITIES is the set of white space-separated lists of tokens, of which each token is in the of . The of ENTITIES is .

The of ENTITIES is scoped to a specific instance document.

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

integer

integer is from by fixing the value of to be 0and disallowing the trailing decimal point. This results in the standard mathematical concept of the integer numbers. The of integer is the infinite set {...,-2,-1,0,1,2,...}. The of integer is .

Lexical representation

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

Canonical representation

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

Derived datatypes nonPositiveInteger

nonPositiveInteger is from by setting the value of to be 0. This results in the standard mathematical concept of the non-positive integers. The of nonPositiveInteger is the infinite set {...,-2,-1,0}. The of nonPositiveInteger is .

Lexical representation

nonPositiveInteger has a lexical representation consisting of an optional preceding sign a negative sign ("-") followed by a finite-length sequence of decimal digits (#x30-#x39). If the sequence of digits consists of all zeros then the sign is optional. 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.

Canonical representation

The canonical representation for nonPositiveInteger is defined by prohibiting certain options from the . Specifically, the negative sign ("-") is required with the token "0" and leading In the canonical form for zero, the sign must be omitted. Leading zeroes are prohibited.

Derived datatypes negativeInteger

negativeInteger is from by setting the value of to be -1. This results in the standard mathematical concept of the negative integers. The of negativeInteger is the infinite set {...,-2,-1}. The of negativeInteger is .

Lexical representation

negativeInteger has a lexical representation consisting of a negative sign ("-") followed by a finite-length sequence of decimal digits (#x30-#x39). For example: -1, -12678967543233, -100000.

Canonical representation

The canonical representation for negativeInteger is defined by prohibiting certain options from the . Specifically, leading zeroes are prohibited.

long

long is from by setting the value of to be 9223372036854775807 and to be -9223372036854775808. The of long is .

Lexical representation

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

Canonical representation

The canonical representation for long is defined by prohibiting certain options from the . Specifically, the the optional "+" sign is prohibited and leading zeroes are prohibited.

Derived datatypes int

int is from by setting the value of to be 2147483647 and to be -2147483648. The of int is .

Lexical representation

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

Canonical representation

The canonical representation for int is defined by prohibiting certain options from the . Specifically, the the optional "+" sign is prohibited and leading zeroes are prohibited.

Derived datatypes short

short is from by setting the value of to be 32767 and to be -32768. The of short is .

Lexical representation

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

Canonical representation

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

Derived datatypes byte

byte is from by setting the value of to be 127 and to be -128. The of byte is .

Lexical representation

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

Canonical representation

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

nonNegativeInteger

nonNegativeInteger is from by setting the value of to be 0. This results in the standard mathematical concept of the non-negative integers. The of nonNegativeInteger is the infinite set {0,1,2,...}. The of nonNegativeInteger is .

Lexical representation

nonNegativeInteger has a lexical representation consisting of an optional sign followed by a 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.

Canonical representation

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

Derived datatypes unsignedLong

unsignedLong is from by setting the value of to be 18446744073709551615. The of unsignedLong is .

Lexical representation

unsignedLong has a lexical representation consisting of a finite-length sequence of decimal digits (#x30-#x39). For example: 0, 12678967543233, 100000.

Canonical representation

The canonical representation for unsignedLong is defined by prohibiting certain options from the . Specifically, leading zeroes are prohibited.

Derived datatypes unsignedInt

unsignedInt is from by setting the value of to be 4294967295. The of unsignedInt is .

Lexical representation

unsignedInt has a lexical representation consisting of a finite-length sequence of decimal digits (#x30-#x39). For example: 0, 1267896754, 100000.

Canonical representation

The canonical representation for unsignedInt is defined by prohibiting certain options from the . Specifically, leading zeroes are prohibited.

Derived datatypes unsignedShort

unsignedShort is from by setting the value of to be 65535. The of unsignedShort is .

Lexical representation

unsignedShort has a lexical representation consisting of a finite-length sequence of decimal digits (#x30-#x39). For example: 0, 12678, 10000.

Canonical representation

The canonical representation for unsignedShort is defined by prohibiting certain options from the . Specifically, the leading zeroes are prohibited.

Derived datatypes unsignedByte

unsignedByte is from by setting the value of to be 255. The of unsignedByte is .

Lexical representation

unsignedByte has a lexical representation consisting of a finite-length sequence of decimal digits (#x30-#x39). For example: 0, 126, 100.

Canonical representation

The canonical representation for unsignedByte is defined by prohibiting certain options from the . Specifically, leading zeroes are prohibited.

positiveInteger

positiveInteger is from by setting the value of to be 1. This results in the standard mathematical concept of the positive integer numbers. The of positiveInteger is the infinite set {1,2,...}. The of positiveInteger is .

Lexical representation

positiveInteger has a lexical representation consisting of an optional positive sign ("+") followed by a finite-length sequence of decimal digits (#x30-#x39). For example: 1, 12678967543233, +100000.

Canonical representation

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

Datatype components

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 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 datatype (schema) components, see Schema Component Details of .

Simple Type Definition

Simple Type definitions provide for:

Establishing the and of a datatype, through the combined set of s specified in the definition;

Attaching a unique name (actually a ) to the and .

The Simple Type Definition Schema Component

The Simple Type Definition schema component has the following properties:

Optional. An NCName as defined by . Either absent or a namespace name, as defined in . One of {atomic, list, union}. Depending on the value of , further properties are defined as follows: atomic A datatype definition (or the simple ur-type definition). list An or simple type definition. union A non-empty sequence of simple type definitions. If the datatype has been by then the component from which it is , otherwise the . A subset of {restriction, list, union}. Optional. An annotation.

Datatypes are identified by their and . Except for anonymous datatypes (those with no ), datatype definitions be uniquely identified within a schema.

If is then the of the datatype defined will be a subset of the of (which is a subset of the of ). If is then the of the datatype defined will be the set of finite-length sequence of values from the of . If is then the of the datatype defined will be the union of the s of each datatype in .

If is then the of must be . If is then the of must be either or . If is then must be a list of datatype definitions.

The value of consists of the set of s specified directly in the datatype definition unioned with the possibly empty set of of .

The value of consists of the set of s and their values.

If is the empty set then the type can be used in deriving other types; the explicit values restriction, list and union prevent further derivations by , and respectively.

XML Representation of Simple Type Definition Schema Components

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

The &v-value; of the name &i-attribute;, if present, otherwise null A set corresponding to the &v-value; of the final &i-attribute;, if present, otherwise of the &v-value; of the finalDefault &i-attribute; of the ancestor schema element information item, if present, otherwise the empty string, as follows: the empty string

the empty set;

#all

{restriction, list, union};

otherwise

a set with members drawn from the set above, each being present or absent depending on whether the string contains an equivalently named space-delimited substring.

Although the finalDefault &i-attribute; of schema may include values other than restriction, list or union, those values are ignored in the determination of

The &v-value; of the targetNamespace &i-attribute; of the parent schema element information item. The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

A datatype can be from a datatype or another datatype by one of three means: by restriction, by list or by union.

Derivation by restriction The &v-value; of of The union of the set of components resolved to by the facet &i-children; merged with from , subject to the Facet Restriction Valid constraints specified in . The component resolved to by the &v-value; of the base &i-attribute; or the &i-children;, whichever is present.

An electronic commerce schema might define a datatype called Sku (the barcode number that appears on products) from the datatype by supplying a value for the facet.

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In this case, Sku is the name of the new datatype, is its and is the facet.

Derivation by list list The component resolved to by the &v-value; of the itemType &i-attribute; or the &i-children;, whichever is present.

A datatype must be from an or a datatype, known as the of the datatype. This yields a datatype whose is composed of finite-length sequences of values from the of the and whose is composed of white space-separated lists of literals of the .

A system might want to store lists of floating point values.

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In this case, listOfFloat is the name of the new datatype, is its and is the derivation method.

As mentioned in , when a datatype is from a datatype, the following s can be used:

regardless of the s that are applicable to the datatype that serves as the of the .

For each of , and , the unit of length is measured in number of list items. The value of is fixed to the value collapse.

Derivation by union union The sequence of components resolved to by the items in the &v-value; of the memberTypes &i-attribute;, if any, in order, followed by the components resolved to by the &i-children;, if any, in order. If is union for any components resolved to above, then the that is replaced by its .

A datatype can be from one or more , or other datatypes, known as the of that datatype.

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 type definition below would accomplish that.

]]> A header

this is a test

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As mentioned in , when a datatype is from a datatype, the only following s can be used:

regardless of the s that are applicable to the datatypes that participate in the

Constraints on XML Representation of Simple Type Definition itemType attribute or simpleType child

Either the itemType &i-attribute; or the &i-child; of the element must be present, but not both.

base attribute or simpleType child

Either the base &i-attribute; or the simpleType &i-child; of the element must be present, but not both.

memberTypes attribute or simpleType children

Either the memberTypes &i-attribute; of the element must be non-empty or there must be at least one simpleType &i-child;.

Simple Type Definition Validation Rules Datatype Valid

A string is datatype-valid with respect to a datatype definition if:

it es a literal in the of the datatype, determined as follows:

if is a member of , then the string must be ;

if is not a member of , then

if is then the string must a literal in the of

if is then the string must be a sequence of white space-separated tokens, each of which es a literal in the of

if is then the string must a literal in the of at least one member of

the value denoted by the literal ed in the previous step is a member of the of the datatype, as determined by it being with respect to each member of (except for ).

Constraints on Simple Type Definition Schema Components list of atomic

If is , then the of be or .

no circular unions

If is , then it is an if and and of any member of .

Simple Type Definition for anySimpleType

There is a simple type definition nearly equivalent to the simple version of the ur-type definition present in every schema by definition. It has the following properties:

anySimpleType http://www.w3.org/2001/XMLSchema the ur-type definition the empty set absent Fundamental Facets equal

Every supports the notion of equality, with the following rules:

for any a and b in the , either a is equal to b, denoted a = b, or a is not equal to b, denoted a != b

there is no pair a and b from the such that both a = b and a != b

for all a in the , a = a

for any a and b in the , a = b if and only if b = a

for any a, b and c in the , if a = b and b = c, then a = c

for any a and b in the if a = b, then a and b cannot be distinguished (i.e., equality is identity)

the s of all datatypes are disjoint (they do not share any values)

Note that a consequence of the above is that, given A and B where A and B are not related by or , for every pair of values a from A and b from B, a != b.

On every datatype, the operation Equal is defined in terms of the equality property of the : for any values a, b drawn from the , Equal(a,b) is true if a = b, and false otherwise.

Note that in consequence of the above:

given A and B where A and B are disjoint, every pair of values a from A and b from B, a != b

two values which are members of the of the same datatype may always be compared with each other

if a datatype T is by from A, B, ... then the of T is the union of s of its A, B, .... Some values in the of T are also values in the of A. Other values in the of T will be values in the of B and so on. Values in the of T which are also in the of A can be compared with other values in the of A according to the above rules. Similarly for values of type T and B and all the other .

if a datatype T' is by from an atomic datatype T then the of T' is a subset of the of T. Values in the s of T and T' can be compared according to the above rules

if datatypes T' and T'' are by from a common atomic ancestor T then the s of T' and T'' may overlap. Values in the s of T' and T'' can be compared according to the above rules

There is no schema component corresponding to the equal .

ordered

An order relation on a is a mathematical relation that imposes a or a on the members of the .

A , and hence a datatype, is said to be ordered if there exists an defined for that .

A partial order is an that is irreflexive, asymmetric and transitive.

A has the following properties:

for no a in the , a < a (irreflexivity)

for all a and b in the , a < b implies not(b < a) (asymmetry)

for all a, b and c in the , a < b and b < c implies a < c (transitivity)

The notation a <> b is used to indicate the case when a != b and neither a < b nor b < a. For any values a and b from different s, a <> b.

When a <> b, a and b are incomparable,otherwise they are comparable.

A total order is an such that for no a and b is it the case that a <> b.

A has all of the properties specified above for , plus the following property:

for all a and b in the , either a < b or b < a or a = b

The fact that this specification does not define an for some datatype does not mean that some other application cannot treat that datatype as being ordered by imposing its own order relation.

provides for:

indicating whether an is defined on a , and if so, whether that is a or a

The ordered Schema Component One of {false, partial, total}.

depends on , and in the component in which a component appears as a member of .

When is , is inherited from of . For all types is as specified in the table in .

When is , is false.

When is , if all members of do not share a common ancestor then is false; if is total for every member of then is total; else if is partial for any member of then is partial; else else is false. is partial unless one of the following:

If every member of is derived from a common ancestor other than the simple ur-type, then is the same as that ancestor's ordered facet

If every member of has a of false for the ordered facet, then is false

bounded

A value u in an U is said to be an inclusive upper bound of a V (where V is a subset of U) if for all v in V, u >= v.

A value u in an U is said to be an exclusive upper bound of a V (where V is a subset of U) if for all v in V, u > v.

A value l in an L is said to be an inclusive lower bound of a V (where V is a subset of L) if for all v in V, l <= v.

A value l in an L is said to be an exclusive lower bound of a V (where V is a subset of L) if for all v in V, l < v.

A datatype is bounded if its has either an or an and either an or and an .

provides for:

indicating whether a is

The bounded Schema Component A .

depends on , and in the component in which a component appears as a member of .

When is , if one of or and one of or are among , then is true; else is false.

When is , if or both of and are among , then is true; else is false.

When is , if is true for every member of and all members of share a common ancestor, then is true; else is false.

cardinality

Every has associated with it the concept of cardinality. Some s are finite, some are countably infinite while still others could conceivably be uncountably infinite (although no defined by this specification is uncountable infinite). A datatype is said to have the cardinality of its .

It is sometimes useful to categorize s (and hence, datatypes) as to their cardinality. There are two significant cases:

s that are finite

s that are countably infinite

provides for:

indicating whether the of a is finite or countably infinite

The cardinality Schema Component One of {finite, countably infinite}.

depends on , and in the component in which a component appears as a member of .

When is and of is finite, then is finite.

When is and of is countably infinite and either of the following conditions are true, then is finite; else is countably infinite:

one of , , is among ,

all of the following are true:

one of or is among

either of the following are true:

is among

is one of , , , , or or any type from them

When is , if or both of and are among , then is finite; else is countably infinite.

When is , if is finite for every member of , then is finite; else is countably infinite.

numeric

A datatype is said to be numeric if its values are conceptually quantities (in some mathematical number system).

A datatype whose values are not is said to be non-numeric.

provides for:

indicating whether a is

The numeric Schema Component A

depends on , , and in the component in which a component appears as a member of .

When is , is inherited from of . For all types is as specified in the table in .

When is , is false.

When is , if is true for every member of , then is true; else is false.

Constraining Facets length

length is the number of units of length, where units of length varies depending on the type that is being from. The value of length be a .

For and datatypes from , length is measured in units of characters as defined in . For , length is measured in units of characters (as for ). For and and datatypes from them, length is measured in octets (8 bits) of binary data. For datatypes by , length is measured in number of list items.

For and datatypes from , 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.

provides for:

Constraining a to values with a specific number of units of length, where units of length varies depending on .

The following is the definition of a 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.

]]> The length Schema Component A . A . Optional. An annotation.

If is true, then types for which the current type is the cannot specify a value for other than .

XML Representation of length Schema Components

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

The &v-value; of the value &i-attribute; The &v-value; of the fixed &i-attribute;, if present, otherwise false The annotations corresponding to all the element information items in the &i-children;, if any. length Validation Rules Length Valid

A value in a is facet-valid with respect to , determined as follows:

if the is then

if is or , then the length of the value, as measured in characters be equal to ;

if is or , then the length of the value, as measured in octets of the binary data, be equal to ;

if is or , then any is facet-valid.

if the is , then the length of the value, as measured in list items, be equal to

The use of on datatypes from and is deprecated. Future versions of this specification may remove this facet for these datatypes.

Constraints on length Schema Components length and minLength or maxLength

It is an for both and either of or to be members of .

If is a member of then

It is an error for to be a member of unless

the of <= the of and

there is type definition from which this one is derived by one or more restriction steps in which has the same and is not specified.

It is an error for to be a member of unless

the of <= the of and

there is type definition from which this one is derived by one or more restriction steps in which has the same and is not specified.

length valid restriction

It is an if is among the members of of and is not equal to the of the parent .

minLength

minLength is the minimum number of units of length, where units of length varies depending on the type that is being from. The value of minLength be a .

For and datatypes from , minLength is measured in units of characters as defined in . For and and datatypes from them, minLength is measured in octets (8 bits) of binary data. For datatypes by , minLength is measured in number of list items.

For and datatypes from , 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.

provides for:

Constraining a to values with at least a specific number of units of length, where units of length varies depending on .

The following is the definition of a datatype which requires strings to have at least one character (i.e., the empty string is not in the of this datatype).

]]> The minLength Schema Component A . A . Optional. An annotation.

If is true, then types for which the current type is the cannot specify a value for other than .

XML Representation of minLength Schema Component

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

A value in a is facet-valid with respect to , determined as follows:

if the is then

if is or , then the length of the value, as measured in characters be greater than or equal to ;

if is or , then the length of the value, as measured in octets of the binary data, be greater than or equal to ;

if is or , then any is facet-valid.

if the is , then the length of the value, as measured in list items, be greater than or equal to

The use of on datatypes from and is deprecated. Future versions of this specification may remove this facet for these datatypes.

Constraints on minLength Schema Components minLength <= maxLength

If both and are members of , then the of be less than or equal to the of .

minLength valid restriction

It is an if is among the members of of and is less than the of the parent .

maxLength

maxLength is the maximum number of units of length, where units of length varies depending on the type that is being from. The value of maxLength be a .

For and datatypes from , maxLength is measured in units of characters as defined in . For and and datatypes from them, maxLength is measured in octets (8 bits) of binary data. For datatypes by , maxLength is measured in number of list items.

For and datatypes from , 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.

provides for:

Constraining a to values with at most a specific number of units of length, where units of length varies depending on .

The following is the definition of a datatype which might be used to accept form input with an upper limit to the number of characters that are acceptable.

]]> The maxLength Schema Component A . A . Optional. An annotation.

If is true, then types for which the current type is the cannot specify a value for other than .

XML Representation of maxLength Schema Components

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

A value in a is facet-valid with respect to , determined as follows:

if the is then

if is or , then the length of the value, as measured in characters be less than or equal to ;

if is or , then the length of the value, as measured in octets of the binary data, be less than or equal to ;

if is or , then any is facet-valid.

if the is , then the length of the value, as measured in list items, be less than or equal to

The use of on datatypes from and is deprecated. Future versions of this specification may remove this facet for these datatypes.

Constraints on maxLength Schema Components maxLength valid restriction

It is an if is among the members of of and is greater than the of the parent .

pattern

pattern is a constraint on the of a datatype which is achieved by constraining the to literals which match a specific pattern. The value of pattern be a .

provides for:

Constraining a to values that are denoted by literals which match a specific .

The following is the definition of a datatype which is a better representation of postal codes in the United States, by limiting strings to those which are matched by a specific .

]]> The pattern Schema Component A . Optional. An annotation. XML Representation of pattern Schema Components

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

be a valid . The &v-value; of the value &i-attribute; The annotations corresponding to all the element information items in the &i-children;, if any. Constraints on XML Representation of pattern Multiple patterns

If multiple element information items appear as &i-children; of a , the &i-value;s should be combined as if they appeared in a single as separate es.

It is a consequence of the schema representation constraint and of the rules for that facets specified on the same step in a type derivation are ORed together, while facets specified on different steps of a type derivation are ANDed together.

Thus, to impose two constraints simultaneously, schema authors may either write a single which expresses the intersection of the two s they wish to impose, or define each on a separate type derivation step.

pattern Validation Rules pattern valid

A literal in a is facet-valid with respect to if:

the literal is among the set of character sequences denoted by the specified in .

enumeration

enumeration constrains the to a specified set of values.

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

provides for:

Constraining a to a specified set of values.

The following example is a datatype definition for a datatype which limits the values of dates to the three US holidays enumerated. This datatype definition would appear in a schema authored by an "end-user" and shows how to define a datatype by enumerating the values in its . The enumerated values must be type-valid literals for the .

some US holidays New Year's day 4th of July Christmas ]]> The enumeration Schema Component A set of values from the of the . Optional. An annotation. XML Representation of enumeration Schema Components

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

be in the of . The &v-value; of the value &i-attribute; The annotations corresponding to all the element information items in the &i-children;, if any. Constraints on XML Representation of enumeration Multiple enumerations

If multiple element information items appear as &i-children; of a the of the component should be the set of all such &i-value;s.

enumeration Validation Rules enumeration valid

A value in a is facet-valid with respect to if the value is one of the values specified in

Constraints on enumeration Schema Components enumeration valid restriction

It is an if any member of is not in the of .

whiteSpace

whiteSpace constrains the of types from such that the various behaviors specified in Attribute Value Normalization in 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 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 leading and trailing #x20's are removed.

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 
, which is the XML character reference to that same UCS code point.

whiteSpace is applicable to all and datatypes. For all datatypes other than (and types by from it) the value of whiteSpace is collapse and cannot be changed by a schema author; for the value of whiteSpace is preserve; for any type by from the value of whiteSpace can be any of the three legal values. For all datatypes by the value of whiteSpace is collapse and cannot be changed by a schema author. For all datatypes by whiteSpace does not apply directly; however, the normalization behavior of types is controlled by the value of whiteSpace on that one of the against which the is successfully validated.

For more information on whiteSpace, see the discussion on white space normalization in Schema Component Details in .

provides for:

Constraining a according to the white space normalization rules.

The following example is the datatype definition for the datatype.

]]> The whiteSpace Schema Component One of {preserve, replace, collapse}. A . Optional. An annotation.

If is true, then types for which the current type is the cannot specify a value for other than .

XML Representation of whiteSpace Schema Components

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

There are no s associated . For more information, see the discussion on white space normalization in Schema Component Details in .

Constraints on whiteSpace Schema Components whiteSpace valid restriction

It is an if is among the members of of and any of the following conditions is true:

is replace or preserve and the of the parent is collapse

is preserve and the of the parent is replace

maxInclusive

maxInclusive is the of the for a datatype with the property. The value of maxInclusive be in the of the .

provides for:

Constraining a to values with a specific .

The following is the definition of a datatype which limits values to integers less than or equal to 100, using .

]]> The maxInclusive Schema Component A value from the of the . A . Optional. An annotation.

If is true, then types for which the current type is the cannot specify a value for other than .

XML Representation of maxInclusive Schema Components

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

be in the of . The &v-value; of the value &i-attribute; The &v-value; of the fixed &i-attribute;, if present, otherwise false, if present, otherwise false The annotations corresponding to all the element information items in the &i-children;, if any. maxInclusive Validation Rules maxInclusive Valid

A value in an is facet-valid with respect to , determined as follows:

if the property in is true, then the value be numerically less than or equal to ;

if the property in is false (i.e., is one of the date and time related datatypes), then the value be chronologically less than or equal to ;

Constraints on maxInclusive Schema Components minInclusive <= maxInclusive

It is an for the value specified for to be greater than the value specified for for the same datatype.

maxInclusive valid restriction

It is an if any of the following conditions is true:

is among the members of of and is greater than the of the parent

is among the members of of and is greater than or equal to the of the parent

is among the members of of and is less than the of the parent

is among the members of of and is less than or equal to the of the parent

maxExclusive

maxExclusive is the of the for a datatype with the property. The value of maxExclusive be in the of the or be equal to in .

provides for:

Constraining a to values with a specific .

The following is the definition of a datatype which limits values to integers less than or equal to 100, using .

]]>

Note that the of this datatype is identical to the previous one (named 'one-hundred-or-less').

The maxExclusive Schema Component A value from the of the . A . Optional. An annotation.

If is true, then types for which the current type is the cannot specify a value for other than .

XML Representation of maxExclusive Schema Components

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

be in the of . The &v-value; of the value &i-attribute; The &v-value; of the fixed &i-attribute;, if present, otherwise false The annotations corresponding to all the element information items in the &i-children;, if any. maxExclusive Validation Rules maxExclusive Valid

A value in an is facet-valid with respect to , determined as follows:

if the property in is true, then the value be numerically less than ;

if the property in is false (i.e., is one of the date and time related datatypes), then the value be chronologically less than ;

Constraints on maxExclusive Schema Components maxInclusive and maxExclusive

It is an for both and to be specified in the same derivation step of a datatype definition.

minExclusive <= maxExclusive

It is an for the value specified for to be greater than the value specified for for the same datatype.

maxExclusive valid restriction

It is an if any of the following conditions is true:

is among the members of of and is greater than the of the parent

is among the members of of and is less than or equal to the of the parent

minExclusive

minExclusive is the of the for a datatype with the property. The value of minExclusive be in the of the or be equal to in .

provides for:

Constraining a to values with a specific .

The following is the definition of a datatype which limits values to integers greater than or equal to 100, using .

]]>

Note that the of this datatype is identical to the previous one (named 'one-hundred-or-more').

The minExclusive Schema Component A value from the of the . A . Optional. An annotation.

If is true, then types for which the current type is the cannot specify a value for other than .

XML Representation of minExclusive Schema Components

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

A value in an is facet-valid with respect to if:

if the property in is true, then the value be numerically greater than ;

if the property in is false (i.e., is one of the date and time related datatypes), then the value be chronologically greater than ;

Constraints on minExclusive Schema Components minInclusive and minExclusive

It is an for both and to be specified for the same datatype.

minExclusive < maxInclusive

It is an for the value specified for to be greater than or equal to the value specified for for the same datatype.

minExclusive valid restriction

It is an if any of the following conditions is true:

is among the members of of and is less than the of the parent

is among the members of of and is greater the of the parent

is among the members of of and is less than the of the parent

is among the members of of and is greater than or equal to the of the parent

minInclusive

minInclusive is the of the for a datatype with the property. The value of minInclusive be in the of the .

provides for:

Constraining a to values with a specific .

The following is the definition of a datatype which limits values to integers greater than or equal to 100, using .

]]> The minInclusive Schema Component A value from the of the . A . Optional. An annotation.

If is true, then types for which the current type is the cannot specify a value for other than .

XML Representation of minInclusive Schema Components

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

A value in an is facet-valid with respect to if:

if the property in is true, then the value be numerically greater than or equal to ;

if the property in is false (i.e., is one of the date and time related datatypes), then the value be chronologically greater than or equal to ;

Constraints on minInclusive Schema Components minInclusive < maxExclusive

It is an for the value specified for to be greater than or equal to the value specified for for the same datatype.

minInclusive valid restriction

It is an if any of the following conditions is true:

is among the members of of and is less than the of the parent

is among the members of of and is greater the of the parent

is among the members of of and is less than or equal to the of the parent

is among the members of of and is greater than or equal to the of the parent

totalDigits

totalDigits controls the maximum number of values in the is the maximum number of digits in values of datatypes from , by restricting it to numbers that are expressible as i × 10^-n where i and n are integers such that |i| < 10^totalDigits and 0 <= n <= totalDigits. The value of totalDigits be a .

The term totalDigits is chosen to reflect the fact that it restricts the to those values that can be represented lexically using at most totalDigits digits. Note that it does not restrict the directly; a lexical representation that adds additional leading zero digits or trailing fractional zero digits is still permitted.

provides for:

Constraining a to values with a specific maximum number of decimal digits (#x30-#x39).

The following is the definition of a datatype which could be used to represent monetary amounts, such as in a financial management application which does not have figures of $1M or more and only allows whole cents. 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 in a manner specific to the (different than specifying max/min values as before).

]]> The totalDigits Schema Component A . A . Optional. An annotation.

If is true, then types for which the current type is the cannot specify a value for other than .

XML Representation of totalDigits Schema Components

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

A value in a is facet-valid with respect to if:

that value is expressible as i × 10^-n where i and n are integers such that |i| < 10^ and 0 <= n <= . the number of decimal digits in the value is less than or equal to ;

Constraints on totalDigits Schema Components totalDigits valid restriction

It is an if is among the members of of and is greater than the of the parent

fractionDigits

fractionDigits controls the size of the minimum difference between values is the maximum number of digits in the fractional part of values in the of datatypes from decimal, by restricting the to numbers that are expressible as i × 10^-n where i and n are integers and 0 <= n <= fractionDigits. The value of fractionDigits be a .

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

provides for:

Constraining a to values with a specific maximum number of decimal digits in the fractional part.

The following is the definition of a 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 .

]]> The fractionDigits Schema Component A . A . Optional. An annotation.

If is true, then types for which the current type is the cannot specify a value for other than .

XML Representation of fractionDigits Schema Components

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

A value in a is facet-valid with respect to if:

that value is expressible as i × 10^-n where i and n are integers and 0 <= n <= . the number of decimal digits in the fractional part of the value is less than or equal to ;

Constraints on fractionDigits Schema Components fractionDigits less than or equal to totalDigits

It is an for to be greater than .

fractionDigits valid restriction

It is an if is among the members of of and is greater than the of the parent .

Conformance

This specification describes two levels of conformance for datatype processors. The first is required of all processors. Support for the other will depend on the application environments for which the processor is intended.

Minimally conforming processors completely and correctly implement the and .

Processors which accept schemas in the form of XML documents as described in (and other relevant portions of ) are additionally said to provide conformance to the XML Representation of Schemas, and , when processing schema documents, completely and correctly implement all s in this specification, and adhere exactly to the specifications in (and other relevant portions of ) for mapping the contents of such documents to schema components for use in validation.

By separating the conformance requirements relating to the concrete syntax of XML schema documents, this specification admits processors which validate using schemas stored in optimized binary representations, dynamically created schemas represented as programming language data structures, or implementations in which particular schemas are compiled into executable code such as C or Java. Such processors can be said to be minimally conforming but not necessarily in conformance to the XML Representation of Schemas.

Schema for Datatype Definitions (normative) DTD for Datatype Definitions (non-normative) Datatypes and Facets ISO 8601 Date and Time Formats ISO 8601 Conventions

The datatypes , , , , , , , and use lexical formats inspired by . Following , the lexical forms of these datatypes can include only the characters #20 through #7F. This appendix provides more detail on the ISO formats and discusses some deviations from them for the datatypes defined in this specification.

"specifies the representation of dates in the proleptic Gregorian calendar and times and representations of periods of time". The proleptic Gregorian calendar includes dates prior to 1582 (the year it came into use as an ecclesiastical calendar). It should be pointed out that the datatypes described in this specification do not cover all the types of data covered by , nor do they support all the lexical representations for those types of data.

lexical formats are described using "pictures" in which characters are used in place of decimal digits. The allowed decimal digits are (#x30-#x39). For the primitive datatypes , , , , , , and . these characters have the following meanings:

C -- represents a digit used in the thousands and hundreds components, the "century" component, of the time element "year". Legal values are from 0 to 9.

Y -- represents a digit used in the tens and units components of the time element "year". Legal values are from 0 to 9.

M -- represents a digit used in the time element "month". The two digits in a MM format can have values from 1 to 12.

D -- represents a digit used in the time element "day". The two digits in a DD format can have values from 1 to 28 if the month value equals 2, 1 to 29 if the month value equals 2 and the year is a leap year, 1 to 30 if the month value equals 4, 6, 9 or 11, and 1 to 31 if the month value equals 1, 3, 5, 7, 8, 10 or 12.

h -- represents a digit used in the time element "hour". The two digits in a hh format can have values from 0 to 2423. If the value of the hour element is 24 then the values of the minutes element and the seconds element must be 00 and 00.

m -- represents a digit used in the time element "minute". The two digits in a mm format can have values from 0 to 59.

s -- represents a digit used in the time element "second". The two digits in a ss format can have values from 0 to 60. In the formats described in this specification the whole number of seconds be followed by decimal seconds to an arbitrary level of precision. This is represented in the picture by "ss.sss". A value of 60 or more is allowed only in the case of leap seconds.

Strictly speaking, a value of 60 or more is not sensible unless the month and day could represent March 31, June 30, September 30, or December 31 in UTC. Because the leap second is added or subtracted as the last second of the day in UTC time, the long (or short) minute could occur at other times in local time. In cases where the leap second is used with an inappropriate month and day it, and any fractional seconds, should considered as added or subtracted from the following minute.

For all the information items indicated by the above characters, leading zeros are required where indicated.

In addition to the above, certain characters are used as designators and appear as themselves in lexical formats.

T -- is used as time designator to indicate the start of the representation of the time of day in .

Z -- is used as time-zone designator, immediately (without a space) following a data element expressing the time of day in Coordinated Universal Time (UTC) in , , , , , , , and .

In the lexical format for the following characters are also used as designators and appear as themselves in lexical formats:

P -- is used as the time duration designator, preceding a data element representing a given duration of time.

Y -- follows the number of years in a time duration.

M -- follows the number of months or minutes in a time duration.

D -- follows the number of days in a time duration.

H -- follows the number of hours in a time duration.

S -- follows the number of seconds in a time duration.

The values of the Year, Month, Day, Hour and Minutes components are not restricted but allow an arbitrary integer. Similarly, the value of the Seconds component allows an arbitrary decimal. Thus, the lexical format for and datatypes derived from it does not follow the alternative format of § 5.5.3.2.1 of .

Truncated and Reduced Formats

supports a variety of "truncated" formats in which some of the characters on the left of specific formats, for example, the century, can be omitted. Truncated formats are, in general, not permitted for the datatypes defined in this specification with three exceptions. The datatype uses a truncated format for which represents an instant of time that recurs every day. Similarly, the and datatypes use left-truncated formats for . The datatype uses a right and left truncated format for .

also supports a variety of "reduced" or right-truncated formats in which some of the characters to the right of specific formats, such as the time specification, can be omitted. Right truncated formats are also, in general, not permitted for the datatypes defined in this specification with the following exceptions: right-truncated representations of are used as lexical representations for , , .

Deviations from ISO 8601 Formats Sign Allowed

An optional minus sign is allowed immediately preceding, without a space, the lexical representations for , , , , .

No Year Zero

The year "0000" is an illegal year value.

More Than 9999 Years

To accommodate year values greater than 9999, more than four digits are allowed in the year representations of , , , and . This follows .

Time zone permitted

The lexical representations for the datatypes , , , , and permit an optional trailing time zone specificiation.

Adding durations to dateTimes

Given a S and a D, this appendix specifies how to compute a E where E is the end of the time period with start S and duration D i.e. E = S + D. Such computations are used, for example, to determine whether a is within a specific time period. This appendix also addresses the addition of s to the datatypes , , , and , which can be viewed as a set of s. In such cases, the addition is made to the first or starting in the set.

This is a logical explanation of the process. Actual implementations are free to optimize as long as they produce the same results. The calculation uses the notation S[year] to represent the year field of S, S[month] to represent the month field, and so on. It also depends on the following functions:

fQuotient(a, b) = the greatest integer less than or equal to a/b

fQuotient(-1,3) = -1

fQuotient(0,3)...fQuotient(2,3) = 0

fQuotient(3,3) = 1

fQuotient(3.123,3) = 1

modulo(a, b) = a - fQuotient(a,b)*b

modulo(-1,3) = 2

modulo(0,3)...modulo(2,3) = 0...2

modulo(3,3) = 0

modulo(3.123,3) = 0.123

fQuotient(a, low, high) = fQuotient(a - low, high - low)

fQuotient(0, 1, 13) = -1

fQuotient(1, 1, 13) ... fQuotient(12, 1, 13) = 0

fQuotient(13, 1, 13) = 1

fQuotient(13.123, 1, 13) = 1

modulo(a, low, high) = modulo(a - low, high - low) + low

modulo(0, 1, 13) = 12

modulo(1, 1, 13) ... modulo(12, 1, 13) = 1...12

modulo(13, 1, 13) = 1

modulo(13.123, 1, 13) = 1.123

maximumDayInMonthFor(yearValue, monthValue) =

M := modulo(monthValue, 1, 13)

Y := yearValue + fQuotient(monthValue, 1, 13)

Return a value based on M and Y:

31	M = January, March, May, July, August, October, or December
30	M = April, June, September, or November
29	M = February AND (modulo(Y, 400) = 0 OR (modulo(Y, 100) != 0) AND modulo(Y, 4) = 0)
28	Otherwise

Algorithm

Essentially, this calculation is equivalent to separating D into <year,month> and <day,hour,minute,second> fields. The <year,month> is added to S. If the day is out of range, it is pinned to be within range. Thus April 31 turns into April 30. Then the <day,hour,minute,second> is added. This latter addition can cause the year and month to change.

Leap seconds are handled by the computation by treating them as overflows. Essentially, a value of 60 seconds in S is treated as if it were a duration of 60 seconds added to S (with a zero seconds field). All calculations thereafter use 60 seconds per minute.

Thus the addition of either PT1M or PT60S to any dateTime will always produce the same result. This is a special definition of addition which is designed to match common practice, and -- most importantly -- be stable over time.

A definition that attempted to take leap-seconds into account would need to be constantly updated, and could not predict the results of future implementation's additions. The decision to introduce a leap second in UTC is the responsibility of the . They make periodic announcements as to when leap seconds are to be added, but this is not known more than a year in advance. For more information on leap seconds, see .

The following is the precise specification. These steps must be followed in the same order. If a field in D is not specified, it is treated as if it were zero. If a field in S is not specified, it is treated in the calculation as if it were the minimum allowed value in that field, however, after the calculation is concluded, the corresponding field in E is removed (set to unspecified).

Months (may be modified additionally below)

temp := S[month] + D[month]

E[month] := modulo(temp, 1, 13)

carry := fQuotient(temp, 1, 13)

Years (may be modified additionally below)

E[year] := S[year] + D[year] + carry

Zone

E[zone] := S[zone]

Seconds

temp := S[second] + D[second]

E[second] := modulo(temp, 60)

carry := fQuotient(temp, 60)

Minutes

temp := S[minute] + D[minute] + carry

E[minute] := modulo(temp, 60)

carry := fQuotient(temp, 60)

Hours

temp := S[hour] + D[hour] + carry

E[hour] := modulo(temp, 24)

carry := fQuotient(temp, 24)

Days

if S[day] > maximumDayInMonthFor(E[year], E[month])

tempDays := maximumDayInMonthFor(E[year], E[month])

else if S[day] < 1

tempDays := 1

else

tempDays := S[day]

E[day] := tempDays + D[day] + carry

START LOOP

IF E[day] < 1

E[day] := E[day] + maximumDayInMonthFor(E[year], E[month] - 1)

carry := -1

ELSE IF E[day] > maximumDayInMonthFor(E[year], E[month])

E[day] := E[day] - maximumDayInMonthFor(E[year], E[month])

carry := 1

ELSE EXIT LOOP

temp := E[month] + carry

E[month] := modulo(temp, 1, 13)

E[year] := E[year] + fQuotient(temp, 1, 13)

GOTO START LOOP

Examples:

dateTime	duration	result
2000-01-12T12:13:14Z	P1Y3M5DT7H10M3.3S	2001-04-17T19:23:17.3Z
2000-01	-P3M	1999-10
2000-01-12	PT33H	2000-01-13

Commutativity and Associativity

Time durations are added by simply adding each of their fields, respectively, without overflow.

The order of addition of durations to instants is significant. For example, there are cases where:

((dateTime + duration1) + duration2) != ((dateTime + duration2) + duration1)

Example:

(2000-03-30 + P1D) + P1M = 2000-03-31 + P1M = 20001-04-30

(2000-03-30 + P1M) + P1D = 2000-04-30 + P1D = 2000-05-01

Regular Expressions

A R is a sequence of characters that denote a set of strings L(R). When used to constrain a , a regular expression R asserts that only strings in L(R) are valid literals for values of that type.

Unlike some popular regular expression languages (including those defined by Perl and standard Unix utilities), the regular expression language defined here implicitly anchors all regular expressions at the head and tail, as the most common use of regular expressions in is to match entire literals. For example, a datatype from such that all values must begin with the character A (#x41) and end with the character Z (#x5a) would be defined as follows:

In regular expression languages that are not implicitly anchored at the head and tail, it is customary to write the equivalent regular expression as:

^A.*Z$

where "^" anchors the pattern at the head and "$" anchors at the tail.

In those rare cases where an unanchored match is desired, including .* at the beginning and ending of the regular expression will achieve the desired results. For example, a datatype from string such that all values must contain at least 3 consecutive A (#x41) characters somewhere within the value could be defined as follows:

A regular expression is composed from zero or more es, separated by | characters.

Regular Expression regExp branch ( '|' branch )*

For all es S, and for all s T, valid s R are: Denoting the set of strings L(R) containing:

(empty string) the set containing just the empty string

S all strings in L(S)

S|T all strings in L(S) and all strings in L(T)

For all es S, and for all s T, valid s R are:	Denoting the set of strings L(R) containing:
(empty string)	the set containing just the empty string
S	all strings in L(S)
S\|T	all strings in L(S) and all strings in L(T)

A branch consists of zero or more s, concatenated together.

Branch branch *

For all s S, and for all es T, valid es R are: Denoting the set of strings L(R) containing:

S all strings in L(S)

ST all strings st with s in L(S) and t in L(T)

For all s S, and for all es T, valid es R are:	Denoting the set of strings L(R) containing:
S	all strings in L(S)
ST	all strings st with s in L(S) and t in L(T)

A piece is an , possibly followed by a .

Piece piece ?

For all s S and non-negative integers n, m such that n <= m, valid s R are: Denoting the set of strings L(R) containing:

S all strings in L(S)

S? the empty string, and all strings in L(S).

S* All strings in L(S?) and all strings st with s in L(S*) and t in L(S). ( all concatenations of zero or more strings from L(S) )

S+ All strings st with s in L(S) and t in L(S*). ( all concatenations of one or more strings from L(S) )

S{n,m} All strings st with s in L(S) and t in L(S{n-1,m-1}). ( All sequences of at least n, and at most m, strings from L(S) )

S{n} All strings in L(S{n,n}). ( All sequences of exactly n strings from L(S) )

S{n,} All strings in L(S{n}S*) ( All sequences of at least n, strings from L(S) )

S{0,m} All strings st with s in L(S?) and t in L(S{0,m-1}). ( All sequences of at most m, strings from L(S) )

S{0,0} The set containing only the empty string

For all s S and non-negative integers n, m such that n <= m, valid s R are:	Denoting the set of strings L(R) containing:
S	all strings in L(S)
S?	the empty string, and all strings in L(S).
S*	All strings in L(S?) and all strings st with s in L(S*) and t in L(S). ( all concatenations of zero or more strings from L(S) )
S+	All strings st with s in L(S) and t in L(S*). ( all concatenations of one or more strings from L(S) )
S{n,m}	All strings st with s in L(S) and t in L(S{n-1,m-1}). ( All sequences of at least n, and at most m, strings from L(S) )
S{n}	All strings in L(S{n,n}). ( All sequences of exactly n strings from L(S) )
S{n,}	All strings in L(S{n}S*) ( All sequences of at least n, strings from L(S) )
S{0,m}	All strings st with s in L(S?) and t in L(S{0,m-1}). ( All sequences of at most m, strings from L(S) )
S{0,0}	The set containing only the empty string

The regular expression language in the Perl Programming Language does not include a quantifier of the form S{,m}, since it is logically equivalent to S{0,m}. We have, therefore, left this logical possibility out of the regular expression language defined by this specification. We welcome further input from implementors and schema authors on this issue.

A quantifier is one of ?, *, +, {n,m} or {n,}, which have the meanings defined in the table above.

Quanitifer quantifier [?*+] | ( '{' '}' ) quantity | | quantRange ',' quantMin ',' QuantExact [0-9]+

An atom is either a , a , or a parenthesized .

Atom atom | | ( '(' ')' )

For all s c, es C, and s S, valid s R are: Denoting the set of strings L(R) containing:

c the single string consisting only of c

C all strings in L(C)

(S) all strings in L(S)

For all s c, es C, and s S, valid s R are:	Denoting the set of strings L(R) containing:
c	the single string consisting only of c
C	all strings in L(C)
(S)	all strings in L(S)

A metacharacter is either ., \, ?, *, +, {, } (, ), [ or ]. These characters have special meanings in s, but can be escaped to form s that denote the sets of strings containing only themselves, i.e., an escaped behaves like a .

A normal character is any XML character that is not a metacharacter. In s, a normal character is an atom that denotes the singleton set of strings containing only itself.

Normal Character Char [^.\?*+()|#x5B#x5D]

Note that a can be represented either as itself, or with a character reference.

Character Classes

A character class is an R that identifies a set of characters C(R). The set of strings L(R) denoted by a character class R contains one single-character string "c" for each character c in C(R).

Character Class charClass | |

A character class is either a or a .

A character class expression is a surrounded by [ and ] characters. For all character groups G, [G] is a valid character class expression, identifying the set of characters C([G]) = C(G).

Character Class Expression charClassExpr '[' ']'

A character group is either a , a , or a .

Character Group charGroup | |

A positive character group consists of one or more s or s, concatenated together. A positive character group identifies the set of characters containing all of the characters in all of the sets identified by its constituent ranges or escapes.

Positive Character Group posCharGroup ( | )+

For all s R, all s E, and all s P, valid s G are: Identifying the set of characters C(G) containing:

R all characters in C(R).

E all characters in C(E).

RP all characters in C(R) and all characters in C(P).

EP all characters in C(E) and all characters in C(P).

For all s R, all s E, and all s P, valid s G are:	Identifying the set of characters C(G) containing:
R	all characters in C(R).
E	all characters in C(E).
RP	all characters in C(R) and all characters in C(P).
EP	all characters in C(E) and all characters in C(P).

A negative character group is a preceded by the ^ character. For all s P, ^P is a valid negative character group, and C(^P) contains all XML characters that are not in C(P).

Negative Character Group negCharGroup '^'

A character class subtraction is a subtracted from a or , using the - character.

Character Class Subtraction charClassSub ( | ) '-'

For any or G, and any C, G-C is a valid , identifying the set of all characters in C(G) that are not also in C(C).

A character range R identifies a set of characters C(R) containing all XML characters with UCS code points in a specified range.

Character Range charRange | | seRange '-' XmlCharRef ( '&#' [0-9]+ ';' ) | (' &#x' [0-9a-fA-F]+ ';' ) charOrEsc | XmlChar [^\#x2D#x5B#x5D] XmlCharIncDash [^\#x5B#x5D]

A single XML character is a that identifies the set of characters containing only itself. All XML characters are valid character ranges, except as follows:

The [, ], - and \ characters are not valid character ranges;

The ^ character is only valid at the beginning of a if it is part of a

The - character is a valid character range only at the beginning or end of a .

The grammar for as given above is ambiguous, but the second and third bullets above together remove the ambiguity.

A also be written in the form s-e, identifying the set that contains all XML characters with UCS code points greater than or equal to the code point of s, but not greater than the code point of e.

s-e is a valid character range iff:

s is a , or an XML character;

s is not \

If s is the first character in a , then s is not ^

e is a , or an XML character;

e is not \ or [; and

The code point of e is greater than or equal to the code point of s;

The code point of a is the code point of the single character in the set of characters that it identifies.

Character Class Escapes

A character class escape is a short sequence of characters that identifies predefined character class. The valid character class escapes are the s, the s, and the s (including the s).

Character Class Escape charClassEsc ( | | | )

A single character escape identifies a set containing a only one character -- usually because that character is difficult or impossible to write directly into a .

Single Character Escape SingleCharEsc '\' [nrt\|.?*+(){}#x2D#x5B#x5D#x5E]

The valid s are: Identifying the set of characters C(R) containing:

\n the newline character (#xA)

\r the return character (#xD)

\t the tab character (#x9)

\\ \

\| |

\. .

\- -

\^ ^

\? ?

\* *

\+ +

\{ {

\} }

$ (

$ )

\[ [

\] ]

The valid s are:	Identifying the set of characters C(R) containing:
`\n`	the newline character (#xA)
`\r`	the return character (#xD)
`\t`	the tab character (#x9)
`\\`	\
`\\|`	\|
`\.`	.
`\-`	-
`\^`	^
`\?`	?
`\*`	*
`\+`	+
`\{`	{
`\}`	}
`\(`	(
`\)`	)
`\[`	[
`\]`	]

specifies a number of possible values for the "General Category" property and provides mappings from code points to specific character properties. The set containing all characters that have property X, can be identified with a category escape \p{X}. The complement of this set is specified with the category escape \P{X}. ([\P{X}] = [^\p{X}]).

Category Escape catEsc '\p{' '}' complEsc '\P{' '}' charProp |

is subject to future revision. For example, the mapping from code points to character properties might be updated. All processors support the character properties defined in the version of that is current at the time this specification became a W3C Recommendation. However, implementors are encouraged to support the character properties defined in any future version.

The following table specifies the recognized values of the "General Category" property.

Category	Property	Meaning
Letters	L	All Letters
	Lu	uppercase
	Ll	lowercase
	Lt	titlecase
	Lm	modifier
	Lo	other

Marks	M	All Marks
	Mn	nonspacing
	Mc	spacing combining
	Me	enclosing

Numbers	N	All Numbers
	Nd	decimal digit
	Nl	letter
	No	other

Punctuation	P	All Punctuation
	Pc	connector
	Pd	dash
	Ps	open
	Pe	close
	Pi	initial quote (may behave like Ps or Pe depending on usage)
	Pf	final quote (may behave like Ps or Pe depending on usage)
	Po	other

Separators	Z	All Separators
	Zs	space
	Zl	line
	Zp	paragraph

Symbols	S	All Symbols
	Sm	math
	Sc	currency
	Sk	modifier
	So	other

Other	C	All Others
	Cc	control
	Cf	format
	Co	private use
	Cn	not assigned

Categories IsCategory | | | | | | Letters 'L' [ultmo]? Marks 'M' [nce]? Numbers 'N' [dlo]? Punctuation 'P' [cdseifo]? Separators 'Z' [slp]? Symbols 'S' [mcko]? Others 'C' [cfon]?

The properties mentioned above exclude the Cs property. The Cs property identifies "surrogate" characters, which do not occur at the level of the "character abstraction" that XML instance documents operate on.

groups code points into a number of blocks such as Basic Latin (i.e., ASCII), Latin-1 Supplement, Hangul Jamo, CJK Compatibility, etc. The set containing all characters that have block name X (with all white space stripped out), can be identified with a block escape \p{IsX}. The complement of this set is specified with the block escape \P{IsX}. ([\P{IsX}] = [^\p{IsX}]).

Block Escape IsBlock 'Is' [a-zA-Z0-9#x2D]+

The following table specifies the recognized block names (for more information, see the "Blocks.txt" file in ).

Start Code	End Code	Block Name	Start Code	End Code	Block Name
#x0000	#x007F	BasicLatin	#x0080	#x00FF	Latin-1Supplement
#x0100	#x017F	LatinExtended-A	#x0180	#x024F	LatinExtended-B
#x0250	#x02AF	IPAExtensions	#x02B0	#x02FF	SpacingModifierLetters
#x0300	#x036F	CombiningDiacriticalMarks	#x0370	#x03FF	Greek
#x0400	#x04FF	Cyrillic	#x0530	#x058F	Armenian
#x0590	#x05FF	Hebrew	#x0600	#x06FF	Arabic
#x0700	#x074F	Syriac	#x0780	#x07BF	Thaana
#x0900	#x097F	Devanagari	#x0980	#x09FF	Bengali
#x0A00	#x0A7F	Gurmukhi	#x0A80	#x0AFF	Gujarati
#x0B00	#x0B7F	Oriya	#x0B80	#x0BFF	Tamil
#x0C00	#x0C7F	Telugu	#x0C80	#x0CFF	Kannada
#x0D00	#x0D7F	Malayalam	#x0D80	#x0DFF	Sinhala
#x0E00	#x0E7F	Thai	#x0E80	#x0EFF	Lao
#x0F00	#x0FFF	Tibetan	#x1000	#x109F	Myanmar
#x10A0	#x10FF	Georgian	#x1100	#x11FF	HangulJamo
#x1200	#x137F	Ethiopic	#x13A0	#x13FF	Cherokee
#x1400	#x167F	UnifiedCanadianAboriginalSyllabics	#x1680	#x169F	Ogham
#x16A0	#x16FF	Runic	#x1780	#x17FF	Khmer
#x1800	#x18AF	Mongolian	#x1E00	#x1EFF	LatinExtendedAdditional
#x1F00	#x1FFF	GreekExtended	#x2000	#x206F	GeneralPunctuation
#x2070	#x209F	SuperscriptsandSubscripts	#x20A0	#x20CF	CurrencySymbols
#x20D0	#x20FF	CombiningMarksforSymbols	#x2100	#x214F	LetterlikeSymbols
#x2150	#x218F	NumberForms	#x2190	#x21FF	Arrows
#x2200	#x22FF	MathematicalOperators	#x2300	#x23FF	MiscellaneousTechnical
#x2400	#x243F	ControlPictures	#x2440	#x245F	OpticalCharacterRecognition
#x2460	#x24FF	EnclosedAlphanumerics	#x2500	#x257F	BoxDrawing
#x2580	#x259F	BlockElements	#x25A0	#x25FF	GeometricShapes
#x2600	#x26FF	MiscellaneousSymbols	#x2700	#x27BF	Dingbats
#x2800	#x28FF	BraillePatterns	#x2E80	#x2EFF	CJKRadicalsSupplement
#x2F00	#x2FDF	KangxiRadicals	#x2FF0	#x2FFF	IdeographicDescriptionCharacters
#x3000	#x303F	CJKSymbolsandPunctuation	#x3040	#x309F	Hiragana
#x30A0	#x30FF	Katakana	#x3100	#x312F	Bopomofo
#x3130	#x318F	HangulCompatibilityJamo	#x3190	#x319F	Kanbun
#x31A0	#x31BF	BopomofoExtended	#x3200	#x32FF	EnclosedCJKLettersandMonths
#x3300	#x33FF	CJKCompatibility	#x3400	#x4DB5	CJKUnifiedIdeographsExtensionA
#x4E00	#x9FFF	CJKUnifiedIdeographs	#xA000	#xA48F	YiSyllables
#xA490	#xA4CF	YiRadicals	#xAC00	#xD7A3	HangulSyllables
#xD800	#xDB7F	HighSurrogates	#xDB80	#xDBFF	HighPrivateUseSurrogates
#xDC00	#xDFFF	LowSurrogates	#xE000	#xF8FF	PrivateUse
#xF900	#xFAFF	CJKCompatibilityIdeographs	#xFB00	#xFB4F	AlphabeticPresentationForms
#xFB50	#xFDFF	ArabicPresentationForms-A	#xFE20	#xFE2F	CombiningHalfMarks
#xFE30	#xFE4F	CJKCompatibilityForms	#xFE50	#xFE6F	SmallFormVariants
#xFE70	#xFEFE	ArabicPresentationForms-B	#xFEFF	#xFEFF	Specials
#xFF00	#xFFEF	HalfwidthandFullwidthForms	#xFFF0	#xFFFD	Specials

The blocks mentioned above exclude the HighSurrogates, LowSurrogates and HighPrivateUseSurrogates blocks. These blocks identify "surrogate" characters, which do not occur at the level of the "character abstraction" that XML instance documents operate on.

is subject to future revision. For example, the grouping of code points into blocks might be updated. All processors support the blocks defined in the version of that is current at the time this specification became a W3C Recommendation. However, implementors are encouraged to support the blocks defined in any future version of the Unicode Standard.

For example, the for identifying the ASCII characters is \p{IsBasicLatin}.

A multi-character escape provides a simple way to identify a commonly used set of characters:

Multi-Character Escape MultiCharEsc '.' | ('\' [sSiIcCdDwW]) WildcardEsc '.'

Character sequence Equivalent

. [^\n\r]

\s [#x20\t\n\r]

\S [^\s]

\i the set of initial name characters, those ed by Letter | '_' | ':'

\I [^\i]

\c the set of name characters, those ed by NameChar

\C [^\c]

\d \p{Nd}

\D [^\d]

\w [#x0000-#x10FFFF]-[\p{P}\p{Z}\p{C}] (all characters except the set of "punctuation", "separator" and "other" characters)

\W [^\w]

Character sequence	Equivalent
.	[^\n\r]
\s	[#x20\t\n\r]
\S	[^\s]
\i	the set of initial name characters, those ed by Letter \| '_' \| ':'
\I	[^\i]
\c	the set of name characters, those ed by NameChar
\C	[^\c]
\d	\p{Nd}
\D	[^\d]
\w	[#x0000-#x10FFFF]-[\p{P}\p{Z}\p{C}] (all characters except the set of "punctuation", "separator" and "other" characters)
\W	[^\w]

The language defined here does not attempt to provide a general solution to "regular expressions" over UCS character sequences. In particular, it does not easily provide for matching sequences of base characters and combining marks. The language is targeted at support of "Level 1" features as defined in . It is hoped that future versions of this specification will provide support for "Level 2" features.

Glossary (non-normative)

The listing below is for the benefit of readers of a printed version of this document: it collects together all the definitions which appear in the document above.

An XSL macro is used to collect definitions from throughout the spec and gather them here for easy reference. References Normative World Wide Web Consortium. XML Base. Available at: http://www.w3.org/TR/2001/REC-xmlbase-20010627/ IEEE. IEEE Standard for Binary Floating-Point Arithmetic. See http://standards.ieee.org/reading/ieee/std_public/description/busarch/754-1985_desc.html World Wide Web Consortium. XML Linking Language (XLink). Available at: &xlink;. Note: only the URI reference escaping procedure defined in Section 5.4 is normatively referenced. &old-xlink; World Wide Web Consortium. Extensible Markup Language (XML) 1.0, Second Edition. Available at: &xmlspec; XML Schema Part 1: Structures. Available at: &xsdl; World Wide Web Consortium. XML Schema Requirements. Available at: http://www.w3.org/TR/1999/NOTE-xml-schema-req-19990215 World Wide Web Consortium. Namespaces in XML. Available at: &xmlnsspec; Tim Berners-Lee, et. al. RFC 2396: Uniform Resource Identifiers (URI): Generic Syntax.. 1998. Available at: http://www.ietf.org/rfc/rfc2396.txt RFC 2732: Format for Literal IPv6 Addresses in URL's. 1999. Available at: http://www.ietf.org/rfc/rfc2732.txt N. Freed and N. Borenstein. RFC 2045: Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies. 1996. Available at: http://www.ietf.org/rfc/rfc2045.txt H. Alvestrand, ed. RFC 1766: Tags for the Identification of Languages 1995. Available at: http://www.ietf.org/rfc/rfc1766.txt H. Alvestrand, ed. RFC 3066: Tags for the Identification of Languages 1995. Available at: http://www.ietf.org/rfc/rfc3066.txt William D Clinger. How to Read Floating Point Numbers Accurately. In Proceedings of Conference on Programming Language Design and Implementation, pages 92-101. Available at: ftp://ftp.ccs.neu.edu/pub/people/will/howtoread.ps The Unicode Consortium. The Unicode Character Database. Available at: http://www.unicode.org/Public/3.1-Update/UnicodeCharacterDatabase-3.1.0.html Non-normative M. Dürst and M. Suignard L. Masinter and M. Durst. Internationalized Resource Identifiers 20022001. Available at: http://www.w3.org/International/iri-edit/draft-duerst-iri-04.txt http://www.ietf.org/internet-drafts/draft-masinter-url-i18n-07.txt World Wide Web Consortium. Ruby Annotation. Available at: http://www.w3.org/TR/2001/WD-ruby-20010216/ World Wide Web Consortium. Hypertext Markup Language, version 4.01. Available at: &html4; World Wide Web Consortium. XML Schema Language: Part 0 Primer. Available at: &primer; Mark Davis. Unicode Regular Expression Guidelines, 1988. Available at: http://www.unicode.org/unicode/reports/tr18/ The Perl Programming Language. See http://www.perl.com/pub/language/info/software.html ISO (International Organization for Standardization). ISO/IEC 9075-2:1999, Information technology --- Database languages --- SQL --- Part 2: Foundation (SQL/Foundation). [Geneva]: International Organization for Standardization, 1999. See http://www.iso.ch/cate/d26197.html International Earth Rotation Service (IERS). See http://maia.usno.navy.mil ISO (International Organization for Standardization). Representations of dates and times, 1988-06-15. Available at: http://www.iso.ch/markete/8601.pdf ISO (International Organization for Standardization). Representations of dates and times, draft revision, 1998. ISO (International Organization for Standardization). Representations of dates and times, draft revision, 2000second edition, 2000-12-15. ISO (International Organization for Standardization). Language-independent Datatypes. See http://www.iso.ch/cate/d19346.html World Wide Web Consortium. RDF Schema Specification. Available at: http://www.w3.org/TR/2000/CR-rdf-schema-20000327/ Information about Leap Seconds Available at: http://tycho.usno.navy.mil/leapsec.990505.html World Wide Web Consortium. Extensible Stylesheet Language (XSL). Available at: http://www.w3.org/TR/2000/CR-xsl-20001121/ Martin J. Dürst and François Yergeau, eds. Character Model for the World Wide Web. World Wide Web Consortium Working Draft. 2001. Available at: &charmod; David M. Gay. Correctly Rounded Binary-Decimal and Decimal-Binary Conversions. AT&T Bell Laboratories Numerical Analysis Manuscript 90-10, November 1990. Available at: http://cm.bell-labs.com/cm/cs/doc/90/4-10.ps.gz Acknowledgements (non-normative)

The following have contributed material to this draftthe first edition of this specification:

Asir S. Vedamuthu, webMethods, Inc Mark Davis, IBM

Co-editor Ashok Malhotra's work on this specification from March 1999 until February 2001 was supported by IBM. From February 2001 until May 2004 it was supported by Microsoft.

The editors acknowledge the members of the XML Schema Working Group, the members of other W3C Working Groups, and industry experts in other forums who have contributed directly or indirectly to the process or content of creating this document. The Working Group is particularly grateful to Lotus Development Corp. and IBM for providing teleconferencing facilities.

The current At the time the first edition of this specification was published, the members of the XML Schema Working Group are were:

Jim Barnette Defense Information Systems Agency (DISA) Paul V. Biron Health Level Seven Don Box DevelopMentor Allen Brown Microsoft Lee Buck TIBCO Extensibility Charles E. Campbell Informix Wayne Carr Intel Peter Chen Bootstrap Alliance and LSU David Cleary Progress Software Dan Connolly W3C staff contact Ugo Corda Xerox Roger L. Costello MITRE Haavard Danielson Progress Software Josef Dietl Mozquito Technologies David Ezell Hewlett-Packard Company Alexander Falk Altova GmbH David Fallside IBM Dan Fox Defense Logistics Information Service (DLIS) Matthew Fuchs Commerce One Andrew Goodchild Distributed Systems Technology Centre (DSTC Pty Ltd) Paul Grosso Arbortext, Inc Martin Gudgin DevelopMentor Dave Hollander Contivo, Inc co-chair Mary Holstege Invited Expert Jane Hunter Distributed Systems Technology Centre (DSTC Pty Ltd) Rick Jelliffe Academia Sinica Simon Johnston Rational Software Bob Lojek Mozquito Technologies Ashok Malhotra Microsoft Lisa Martin IBM Noah Mendelsohn Lotus Development Corporation Adrian Michel Commerce One Alex Milowski Invited Expert Don Mullen TIBCO Extensibility Dave Peterson Graphic Communications Association Jonathan Robie Software AG Eric Sedlar Oracle Corp. C. M. Sperberg-McQueen W3C co-chair Bob Streich Calico Commerce William K. Stumbo Xerox Henry S. Thompson University of Edinburgh Mark Tucker Health Level Seven Asir S. Vedamuthu webMethods, Inc Priscilla Walmsley XMLSolutions Norm Walsh Sun Microsystems Aki Yoshida SAP AG Kongyi Zhou Oracle Corp.

The XML Schema Working Group has benefited in its work from the participation and contributions of a number of people not currently members of the Working Group, including in particular those named below. Affiliations given are those current at the time of their work with the WG.

Paula Angerstein Vignette Corporation David Beech Oracle Corp. Gabe Beged-Dov Rogue Wave Software Greg Bumgardner Rogue Wave Software Dean Burson Lotus Development Corporation Mike Cokus MITRE Andrew Eisenberg Progress Software Rob Ellman Calico Commerce George Feinberg Object Design Charles Frankston Microsoft Ernesto Guerrieri Inso Michael Hyman Microsoft Renato Iannella Distributed Systems Technology Centre (DSTC Pty Ltd) Dianne Kennedy Graphic Communications Association Janet Koenig Sun Microsystems Setrag Khoshafian Technology Deployment International (TDI) Ara Kullukian Technology Deployment International (TDI) Andrew Layman Microsoft Dmitry Lenkov Hewlett-Packard Company John McCarthy Lawrence Berkeley National Laboratory Murata Makoto Xerox Eve Maler Sun Microsystems Murray Maloney Muzmo Communication, acting for Commerce One Chris Olds Wall Data Frank Olken Lawrence Berkeley National Laboratory Shriram Revankar Xerox Mark Reinhold Sun Microsystems John C. Schneider MITRE Lew Shannon NCR William Shea Merrill Lynch Ralph Swick W3C Tony Stewart Rivcom Matt Timmermans Microstar Jim Trezzo Oracle Corp. Steph Tryphonas Microstar

The lists given above pertain to the first edition. At the time work on this second edition was completed, the membership of the Working Group was:

Leonid Arbouzov Sun Microsystems Jim Barnette Defense Information Systems Agency (DISA) Paul V. Biron Health Level Seven Allen Brown Microsoft Charles E. Campbell Invited expert Peter Chen Invited expert Tony Cincotta NIST David Ezell National Association of Convenience Stores Matthew Fuchs Invited expert Sandy Gao IBM Andrew Goodchild Distributed Systems Technology Centre (DSTC Pty Ltd) Xan Gregg Invited expert Mary Holstege Mark Logic Mario Jeckle DaimlerChrysler Marcel Jemio Data Interchange Standards Association Kohsuke Kawaguchi Sun Microsystems Ashok Malhotra Invited expert Lisa Martin IBM Jim Melton Oracle Corp Noah Mendelsohn IBM Dave Peterson Invited expert Anli Shundi TIBCO Extensibility C. M. Sperberg-McQueen W3C co-chair Hoylen Sue Distributed Systems Technology Centre (DSTC Pty Ltd) Henry S. Thompson University of Edinburgh Asir S. Vedamuthu webMethods, Inc Priscilla Walmsley Invited expert Kongyi Zhou Oracle Corp.

We note with sadness the accidental death of Mario Jeckle shortly after the completion of work on this document. In addition to those named above, several people served on the Working Group during the development of this second edition:

Oriol CarboUniversity of Edinburgh Tyng-Ruey ChuangAcademia Sinica Joey CoyleHealth Level 7 Tim EwaldDevelopMentor Nelson Hung Corel Melanie Kudela Uniform Code Council Matthew MacKenzieXML Global Cliff SchmidtMicrosoft John StantonDefense Information Systems Agency John Tebbutt NIST Ross Thompson Contivo Scott VorthmannTIBCO Extensibility