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XML Schema Part 2: Datatypes datatypes-&iso.doc.date; W3C Candidate Recommendation ⅆ&MM;&year;

(in XML and HTML, with a schema and DTD including datatype definitions, as well as a schema for built-in datatypes only, in a separate namespace.)

http://www.w3.org/TR/2000/CR-xmlschema-2-20001024/ http://www.w3.org/TR/2000/WD-xmlschema-2-20000922/ http://www.w3.org/TR/xmlschema-2/ Paul V. Biron Kaiser Permanente, for Health Level Seven Paul.V.Biron@kp.org Ashok Malhotra IBM petsa@us.ibm.com

This specification of the XML Schema language is a Candidate Recommendation of the World Wide Web Consortium. This means that the XML Schema Working Groupconsiders the specification to be stable and encourages implementation and comment on the specification during this period. The Candidate Recommendation review period ends on 15 December 2000. Please send review comments before the review period ends to www-xml-schema-comments@w3.org (public mailing list archive).

During the Candidate Recommendation phase, although feedback based on any aspect of implementation experience is welcome, there are certain aspects of the design presented herein for which the Working Group is particularly interested in feedback. These are designated priority feedback aspects of the design, and identified as such in editorial notes throughout this draft.

Should this specification prove very difficult or impossible to implement, the Working Group will return the document to Working Draft status and make necessary changes. Otherwise, the Working Group anticipates asking the W3C Director to advance this document to Proposed Recommendation.

This document has been produced as part of the W3C XML Activity. The authors of this document are the XML Schema WG members. Different parts of this specification have different editors.

A list of current W3C working drafts can be found at http://www.w3.org/TR/. They may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use W3C Working Drafts as reference material or to cite them as other than "work in progress".

Several "note types" are used throughout this draft:

something on which the editors are seeking comment.

something the editors wish to call to the attention of the reader. To be removed prior to the recommendation becoming final.

something the editors wish to call to the attention of the reader. To remain in the final recommendation as non-normative text.

XML Schema: Datatypes is part 2 of the specification of the XML Schema language. It defines facilities for defining datatypes to be used 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 2000-09-28: PVB: fixed syntax errors in example schemas for "Derivation by Union" and "enumeration" facet. 2000-09-28: PVB: fixed typos in content models of restriction, list and union in section "XML Representation of Datatype Definitions". Still need to fix stylesheet to correctly generate "List of QName" for the type of the memberTypes attribute on union. 2000-09-28: PVB: fixed typo in section on equality, where "restriction" was left out of the final sentence, beginning "By definition". 2000-09-28: PVB: added appropriate definitions for a list's "itemType" and a union's "memberTypes". 2000-09-28: PVB: folded old Constraint on Schemas: length and maxLength into the existing Constraint on Schemas: length and minLength 2000-09-28: PVB: fixed many typos as reported by Wayne Carr in post on 2000-09-17. 2000-09-29: PVB: fixed NOTATION datatype, by requiring at least one enumeration facet and further requiring that all enumeration facets name a declared notation. Folded the old "NOTATION declared" constraint into a new COS: "enumeration required for NOTATION" 2000-09-29: PVB: changed SVC "encoding required" to a COS. 2000-09-29: PVB: implemented WG decision in LC-7: minimum number of decimal digits for precision. 2000-09-29: PVB: started removing inconsistencies introduced by the presence of list and union as derivation methods: i.e., it is no longer the case that all derived types have a base type, it is only those types derived by restriction that do (lists have itemType's, while unions have memberTypes). Still have much more to clean up in this regard tho, including rework in sections 4.1 and 5.1. 2000-09-29: PVB: updated the schema and datatypes namespaces to be consistent with the Hawthorne votes 2000-10-02: AM: fixed value space for recurring duration. 2000-10-02: AM: added info about timeDuration to Appendix D. 2000-10-02: AM: rewrote order property for timeDuration and recurringDuration. 2000-10-02: AM: added canonical lexical forms for list and union. 2000-10-04: PVB: minor editorial fix in prose describing recurringDuration and timeDuration 2000-10-04: PVB: fixed lexical space of NOTATION to be the set of names of declared NOTATIONs and added the fact that NOTATION is derived from QName. 2000-10-05: PVB: added S{n} to the regex language, which should have been there all the time (equiv to S{n,n}) 2000-10-06: PVB: added whiteSpace facet, component def and XML Rep for it. 2000-10-06: PVB: changed the initial wording of CVC Datatype Valid to say that "a string is..." instead of "a sequence of char info items is...". Makes the spec more generally applicable. 2000-10-06: PVB: flushed out schema components and XML representation/ property mapping, to encorporate derivation by restriction, list and union 2000-10-06: PVB: sync'd the acknowledgement sections with Part 1 2000-10-06: PVB: flushed out the schema for datatypes, such that all datatype definitions have an id attribute, all elements involved in datatype definitions also now have an id attribute. Each built-in datatype definition has a documentation annotation that points to the section of the spec where that datatype is described; each element used for facets also has a documentation annotation that points to the section of the spec where that facet is defined. 2000-10-11: PVB: fixed bug in SVC that said that union/@memberTypes and union/child::simpleType were mutually exclusive...the corrected constraint is simply that at least one of them must be valued. 2000-10-11: PVB: fixed the broken link on the XML Rep for union, to point to the Datatype Definition component (there is no union component). 2000-10-16: PVB: clarified property mapping for memberTypes property in the XML Rep of the Union Element Information Item for Datatype Definitions. 2000-10-16: PVB: fixed typo on the XML Rep of the Union Element Information Item that incorrectly referred to a "union" schema component. 2000-10-16: PVB: fixed many broken links 2000-10-16: PVB: added xml:lang='en' to all documentation elements in the schema for datatypes 2000-10-18: PVB: fixed typo in century which said that 20 was the lexical for the 19th century...it is now 19 is the literal for 20th century 2000-10-18: PVB: fixed copy-paste typos in specification of min/maxLength facet, which said just "length" in several places 2000-10-18: PVB: removed mention of character info items in the definition of lexical space (and literal) 2000-10-18: PVB: cleared up ambiguous (many) uses of the word "may" that were not used in the sense of the term "may" in the Terminology section...made sure that all correct uses of "may" were linked to the definition 2000-10-18: PVB: definition of match aligned with XML 1.0 2e 2000-10-18: PVB: changed string length-related facets to be measured in terms of XML 1.0 characters instead of code points 2000-10-18: PVB: added note to string length-related facets stating that length may not be what some users perceive as the "string length" 2000-10-18: PVB: changed example in description of hex encoding to something more "binary" 2000-10-18: PVB: clarified value space of string in terms of XML 1.0 characters. 2000-10-18: PVB: fixed (thought this was already done, but I guess not) Appdx D to note that hours range form 0-23, minutes from 0-59 and seconds from 0-59 or 0-60 in the case of leap seconds. 2000-10-18: PVB: definition of language now references the "Language Identifiers" section in XML 1.02e instead of the LanguageID production (which is gone in 2e). 2000-10-18: PVB: added a PFR requesting advice on whether future versions should allow embedded white space in regex's. 2000-10-18: PVB: removed Cs property from regex language and added note stating why it is the only property not allowed 2000-10-18: PVB: fixed typo in character range expansion of \w escape in the regex language 2000-10-18: PVB: now sites XML 1.0 2e and Unicode 3 normatively, and ISO 10646 and Unicode 2 non-normatively. 2000-10-18: PVB: added note stating that conforming processors are only required to support the Unicode char props and block names in the regex language are are current at the time this spec goes to Rec, but that implementors are encouraged to provide access to future revisions to Unicode. 2000-10-18: PVB: added note about possible future support for "Level 2" in regex's 2000-10-18: PVB: changed body-temp example from fahrenheit to celsius 2000-10-18: PVB: added xml:lang='en' to all documentation annotations in the schema for datatypes 2000-10-19: PVB: added note to the effect that recurringDuration won't meet the needs of all calendaring/scheduling applications 2000-10-19: PVB: added PFR to recurringDuration asking for interop feedback not just between schema processors but with other date/time systems 2000-10-19: PVB: added PFR regarding order-relation on timeDuration 2000-10-19: PVB: added note on uriReference about hex encoding and possible "out-of-sync" problems with XMl 1.0, XPointer and CharMod. 2000-10-19: PVB: removed ednote on pattern for binary
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 IBM 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 & Java primitive data types, 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:

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

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

(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.

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

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

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

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:

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.

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

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 .

Facets

A facet is a single defining aspect of a . Generally speaking, each facet characterizes a along independent axes or dimensions.

The facets of a datatype serve to distinguish those aspects of one datatype which differ from other datatypes. Rather than being defined solely in terms of a prose description the datatypes in this specification are defined in terms of the synthesis of facet values which together determine the and properties of the datatype.

Facets are of two types: fundamental facets that define the datatype and non-fundamental or constraining facets that constrain the permitted values of a datatype.

Fundamental facets

A fundamental facet is an abstract property which serves to semantically characterize the values in a .

These properties are discussed in this section.

Equal

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

for any two instances of values from the (a,b), either a is equal to b, denoted a = b, or a is not equal to b, denoted a != b;

there is no pair of instances (a, b) of values from the such that both a = b and a != b;

for every value a from the , a = a;

for any two instances (a, b) of values from the , a = b if and only if b = a;

for any three instances (a, b, c) of values from the , if a = b and b = c, then a = c.

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.

By definition, given  A and  B where A and B are not related by restriction, for every pair of values a from A and b from B, a != b.

Order

An order relation on a is a mathematical relation which imposes a total order on the members of the .

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

order relations have the following rules:

for every pair (a, b) from the , either a < b or b < a, or a = b;

for every triple (a, b, c) from the , if a < b and b < c, then a < c.

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.

Bounds

A is bounded above if there exists a unique value U in the such that, for all values v in the , v <= U. The value U is said to be an upper bound of the .

A is bounded below if there exists a unique value L in the space such that, for all values v in the , L <= v. The value L is then said to be a lower bound of the .

A datatype is bounded if its has both an and a .

Cardinality

Every has associated with it the concept of cardinality. Some s are finite, some are countably infinite while still others are uncountably 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

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.

Constraining or Non-fundamental facets

A constraining facet is an optional property that can be applied to a datatype to constrain its .

Constraining the consequently constrains the . Adding s to a is described in .

In this section we define all s that are available for use when defining datatypes.

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 and datatypes from , length is measured in octets (8 bits) of binary data. For datatypes by , length is measured in 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.

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 datatypes from , minLength is measured in octets (8 bits) of binary data. For datatypes by , minLength is measured in 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.

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 datatypes from , maxLength is measured in octets (8 bits) of binary data. For datatypes by , maxLength is measured in 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.

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 .

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 that from which it is .

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}.

No normalization is done, the value is not changed (this is the behavior required by for element content)

All occurrences of #x9 (tab), #xA (linefeed) and #xD (carriage return) are replaced with #x20 (space)

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 Code Set (UCS) code point hexidecimal A (linefeed), which is denoted by U+000A in . This notation is to be distinguished from &#xA;, which is the XML character reference to that same UCS code point.

whiteSpace is applicable to all and datatypes. For all datatypes other than (and types by restriction 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 restriction 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 .

maxInclusive

maxInclusive is the of the for a datatype with the property. The value is inclusive in the sense that the value is itself included in the . The value of maxInclusive  be of the same type as the .

maxExclusive

maxExclusive is the of the for a datatype with the property. The value is exclusive in the sense that the value is itself excluded from the . The value of maxExclusive must be of the same type as the .

minInclusive

minInclusive is the of the for a datatype with the property. The value is inclusive in the sense that the value is itself included in the . The value of minInclusive must be of the same type as the .

minExclusive

minExclusive is the of the for a datatype with the property. The value is exclusive in the sense that the value is itself excluded from the for the datatype. The value of minExclusive  be of the same type as the .

precision

precision is the maximum number of decimal digits in values of datatypes from . The value of precision  be a .

scale

scale is the maximum number of decimal digits in the fractional part of values of datatypes from . The value of scale   be a .

encoding

encoding is the encoded form of the of datatypes from . The value of encoding  be one of {hex, base64}.

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

If the value of encoding is base64 then the entire binary stream is encoding using the Base64 Content-Transfer-Encoding defined in Section 6.8 .

duration

duration is the duration of values for the datatype and datatypes from . The value of duration   be a .

period

period is the frequency of recurrence for values for the datatype and datatypes from . The value of period   be .

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 I know, now this is a trichotomy and not a dichotomy...hopefully no one will be picky enough to complain

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 which consists of a finite-length sequence of values of an datatype.

Union datatypes are those whose s and s are the union of the s and s of two 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 whitespace separated sequence of literals of the datatype of the items in the (where whitespace es S in ).

The 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. 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 can be used:

For each of the above s, the unit of length is measured in number of list items.

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.

]]>

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. See and for more details.

PVB Do we want to make the restriction that there has to be more than one type in a union? It was in the proposal, but I don't think it should be an error if only one appears.

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 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.

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 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 such usage the datatypes in this specification have the namespace URI:

http://www.w3.org/2000/10/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 ).

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 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 its .

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 Code Set code point (, and ), which is an integer.

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

Constraining facets 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 lexical values {true, false}.

Constraining facets float

float corresponds 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 special values: positive and negative zero, positive negative infinity and not-a-number. The on float is: x < y iff y - x is positive.

A literal in the representing a decimal number d maps to the normalized value in the of float 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

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 0, -0, INF, -INF and NaN, respectively.

For example, -1E4, 1267.43233E12, 12.78e-2, 12 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 preceding optional "+" sign is prohibited from the mantissa. The exponent must be indicated by "E" and number representations must be normalized such that for non-zero numbers there is a single non-zero digit to the left of the decimal point. Leading and trailing zeroes are disallowed in the mantissa and leading zeroes are disallowed in the exponent.

Constraining facets double

The double datatype 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 special values: positive and negative zero, positive negative infinity and not-a-number. The on double is: x < y iff y - x is positive.

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.

The special values positive and negative zero, positive and negative infinity and not-a-number have 0, -0, INF, -INF and NaN, respectively.

For example, -1E4, 1267.43233E12, 12.78e-2, 12 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 preceding optional "+" sign is prohibited from the mantissa. The exponent must be indicated by "E" and number representations must be normalized such that for non-zero numbers there is a single non-zero digit to the left of the decimal point. Leading and trailing zeroes are disallowed in the mantissa and leading zeroes are disallowed in the exponent.

Constraining facets decimal

decimal represents arbitrary precision decimal numbers. The of decimal is the set of the values i × 10^-n, where i and n are integers such that n >= 0. The on decimal is: 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.

As in all such cases, the minimum number of decimal digits that all processors support is too small for some applications and, perhaps, too large for others. We welcome further input from implementors whether the minimum value of 18 is acceptable. 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, in accordance with the scale and precision facets, with an optional leading sign. 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.

Canonical representation

The canonical representation for decimal is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited. Leading zeroes are prohibited. Trailing zeroes to the right of the decimal point are also prohibited.

Constraining facets Derived datatypes timeDuration

timeDuration represents a duration of time. The of timeDuration 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. The on timeDuration is defined as follows. For timeDuration t and starting  s, compute an end  t[s] whose components CCYY, MM, DD, etc. are computed by adding to those components of s the corresponding components of t and handling the carry-overs correctly. Then, the of two timeDuration values x and y is x > y iff x[s] > y[s] for any starting instant s, x < y iff x[s] < y[s] for any s and x = y iff x[s] = y[s] for any s.

Note that the on timeDuration holds for some s but not for all s. In such cases the the order relation in said to be indeterminate. For example, while P1M25D > P50D and P1M10D < P50 the order relation between P1M20D and P50D is indeterminate.

The complexity of real world durations of time introduces difficulties into any design that attempts to support them. The XML Schema Working Group acknowledges the undesirability of an that specifies a partial (as opposed to a total) order; however, it has found no other solution that garnered consensus. Therefore, the XML Schema Working Group welcomes feedback from implementors and schema authors on alternative designs. Specifically, we are interested in knowing whether timeDuration needs to be at all and in hearing how other implemented systems which provide a total order for durations of time have defined that total order. Lexical representation

The lexical representation for timeDuration 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 integer. Similarly, the value of the Seconds component allows an arbitrary decimal. Thus, the lexical representation of timeDuration 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:

The lowest order items be omitted. If omitted their value is assumed to be zero.

The lowest order item have a decimal fraction.

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 must be present.

The designator 'T' shall be absent 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.

Constraining facets recurringDuration

recurringDuration represents a specific period of time that recurs with a specific frequency, starting from a specific point in time. The value that appears in an instance document is interpreted as the point in time when the recurrence begins. The of recurringDuration is the set of sets of s that recur with a specific starting from a specific . The on recurringDuration is: x < y iff y - x is positive where x and y are starting s. recurringDurations which have different values for the duration and period cannot be compared.

recurringDuration has two constraining facets and whose values be specified when the datatype is defined. These facets specify the length of the duration and after what duration it recurs. The lexical format used to specify these facet values is the lexical format for . A value of 0 for the facet means that the duration does not recur i.e. there is but a single occurrence. A value of 0 for the facet means that the duration is, in fact, a single instant of time.

recurringDuration is a conceptual datatype which serves as a from which the other date and time datatypes are . It can also be used as a for datatypes. A datatype can be from recurringDuration by specifying values for and .

While recurringDuration is capable of serving as the of datatypes used in many different date and time related applications beyond those supplied by its use as the of the datatypes from it, recurringDuration is not intended as a general-purpose solution to calendaring and scheduling applications.

The XML Schema Working Group is particularly interested in feedback from implementors and schema authors as to how , recurringDuration and the other date and time related datatypes from recurringDuration interoperate with other date and time related systems. duration and period required for recurringDuration

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

Lexical representation

A single lexical representation, which is a subset of the lexical representations allowed by , is allowed for recurringDuration. This lexical representation is the extended format CCYY-MM-DDThh:mm:ss.sss where "CC" represents the century, "YY" the year, "MM" the month and "DD" the day, preceded by an optional leading sign to indicate a negative number. If the sign is omitted, "+" is assumed. The letter "T" is the date/time separator and "hh", "mm", "ss.sss" represent hour, minute and second respectively. Additional digits can be used to increase the precision of fractional seconds if desired. To accommodate year values greater than 9999 additional digits can be added to the left of this representation. The year 0000 is prohibited.

This representation can be immediately followed by a "Z" to indicate Coordinated Universal Time (UTC). To indicate the time zone, i.e. the difference between the local time and Coordinated Universal Time, the difference immediately follows the time and consists of a sign, + or -, followed by hh:mm. See also .

The derived datatype uses the same lexical representation. Other derived datatypes , , and use truncated versions of this lexical representation.

Canonical representation

The canonical representation for recurringDuration is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal Time (UTC) and be indicated by a "Z".

Constraining facets Derived datatypes binary

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

encoding required for binary

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

Constraining facets uriReference

uriReference represents a Uniform Resource Identifier (URI) Reference as defined in Section 4 of , as amended by . A uriReference can be an or a , and have an optional fragment identifier.

URI References require certain ASCII characters and all non-ASCII characters be hex encoded, sometimes called URI-escaping (see Section 2 of , as amended by Section 3 of ). Therefore, schema authors need to exercise caution in the use of uriReference. Specifically, schema authors should avoid uriReference in cases where literals should be allowed to directly contain characters that , as amended by , require to be hex encoded.

There is ongoing discussion about how to treat URI References that might contain non-ASCII characters. It is extremely important that all W3C specifications that deal with such URI References (at least this specification, , and , probably others) be aligned; however, it is not clear how best to achieve that alignment with this specification. In addition to the current design, where both the and of uriReference are considered to be hex encoded, there are at least 3 alternative designs that could be considered: 1) have 2 types, the current type and another type (not strictly speaking, a URI Reference) where both the and where allowed to contain non-ASCII characters; 2) a single type whose is allowed to contain non-ASCII characters, but whose was the set of hex-encoded literals; 3) a single type whose was hex-encoded, but whose was allowed to contain non-ASCII characters (i.e., the set of hex-decoded literals). The XML Schema Working Group welcomes feedback from implementors and schema authors on how to further harmonize the effected specifications; in particular, we seek advice on which of the above alternatives (or some other alternative not yet considered) is most desirable. Changes resulting from such further harmonization might result in additional changes to the XML Schema Language in cases where uriReference in used (e.g., xsi:schemaLocation in ).

An absolute uriReference refers to a resource in a manner which is independent of the context in which the occurs.

A relative uriReference refers to a resource by describing the difference within a hierarchy of resources between the context in which the relative uriReference occurs and the of the resource.

Lexical representation

The of uriReference is the set of strings that the URI-reference production in Section 4 of .

Constraining facets ID

ID represents the ID attribute type from . The of ID is the set of all strings that the NCName production in and have been used in an XML document. The of ID is the set of all strings that the NCName production in .

The of ID is scoped to a specific instance document.

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

ID Unique

An ID  not appear more than once in an XML document as a value of this type; i.e., ID values must uniquely identify the elements which bear them.

Constraining facets IDREF

IDREF represents the IDREF attribute type from . The of IDREF is the set of all strings that the NCName production in and have been used in an XML document as the value of an element or attribute of type . The of IDREF is the set of strings that the NCName production in .

The of IDREF is scoped to a specific instance document.

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

IDREF

An IDREF   the value of an in the XML document in which it occurs.

Constraining facets Derived datatypes 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 scoped to a specific instance document.

ENTITY declared

ENTITY values   an unparsed entity name that is declared in the schema.

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

Constraining facets Derived datatypes QName

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

Constraining facets Derived datatypes 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 .

CDATA

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

Constraining facets Derived datatypes token

token represents tokenized strings. The of token is the set of strings that do not contain the 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 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 .

Constraining facets Derived datatypes language

language represents natural language identifiers as defined 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 are valid language identifiers as defined in the language identification section of . The of language is .

Constraining facets IDREFS

IDREFS represents the IDREFS attribute type from . The of IDREFS is the set of finite-length sequences of s that have been used in an XML document. The of IDREFS is the set of whitespace separated tokens, each of which is in the of . The of IDREFS is .

The of IDREFS is scoped to a specific instance document.

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

Constraining facets ENTITIES

ENTITIES represents the ENTITIES attribute type from . The of ENTITIES is the set of finite-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 tokens, each of which 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.

Constraining facets 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.

Constraining facets Derived datatypes NMTOKENS

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

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

Constraining facets 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 .

Constraining facets 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 .

Constraining facets NOTATION

NOTATION represents the NOTATION attribute type from . The of NOTATION is the set of all names of notations declared in the current schema. The of NOTATIONis the set of all names of notations declared in the current schema. The of NOTATION is .

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. Furthermore, the value of all facets must the name of a notation declared in the current schema.

The of NOTATION is scoped to a specific schema, given the requirement that all values of the facet must be the name of a declared notation.

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

Constraining facets integer

integer is from by fixing the value of to be 0. 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.

Constraining facets 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 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. 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 zeroes are prohibited.

Constraining facets 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.

Constraining facets &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.

Constraining facets Derived datatypes ∫

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

Lexical representation

∫ 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 ∫ is defined by prohibiting certain options from the . Specifically, the the optional "+" sign is prohibited and leading zeroes are prohibited.

Constraining facets 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.

Constraining facets 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.

Constraining facets 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, "+" is assumed. 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.

Constraining facets 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.

Constraining facets 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.

Constraining facets 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.

Constraining facets 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.

Constraining facets 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 the optional "+" sign is prohibited and leading zeroes are prohibited.

Constraining facets timeInstant

timeInstant represents a specific instant of time. The of timeInstant is the space of Combinations of date and time of day values as defined in § 5.4 of . The of timeInstant is . timeInstant is generated from by fixing the value of the facet equal to "P0Y" and the value of the facet equal to "P0Y" (no recurrence).

Lexical representation

A single lexical representation, which is a subset of the lexical representations allowed by , and is the same lexical representation as its basetype is allowed for timeInstant.

For example, to indicate 1:20 pm on May the 31st, 1999 for Eastern Standard Time which is 5 hours behind Coordinated Universal Time (UTC), one would write: 1999-05-31T13:20:00-05:00.

Canonical representation

The canonical representation for timeInstant is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal Time (UTC) and be indicated by a "Z".

Constraining facets 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 instances e.g. lexical 12:30:24 to represent T12:30:24 on any day. The of time is . time is generated from by fixing the value of the facet equal to "P0Y" and the value of the facet equal to "P1D".

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, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal Time (UTC) and be indicated by a "Z".

Constraining facets timePeriod

timePeriod represents a specific period of time with a given start and end. The of timePeriod is the value space of Periods of time as defined in § 5.5 of . The of timePeriod is . timePeriod is generated from by fixing the value of the facet equal to "P0Y" (no recurrence).

The value in the instance specifies the start of the time period while the value of facet, specified when subtypes are defined, gives the duration of the time period.

Lexical representation

The lexical representation for timePeriod is the same as that of its basetype, .

Canonical representation

The canonical representation for timePeriod is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal Time (UTC) and be indicated by a "Z".

Constraining facets period facet value required for timePeriod

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

Derived datatypes date

date represents a that starts at midnight of a specified day and lasts until midnight the following day. The of date is the set of Gregorian calendar dates as defined in § 5.2.1 of . Specifically, it is a set of one-day long, non-periodic instances e.g. lexical 1999-10-26 to represent the whole day of 1999-10-26, independent of how many hours this day has. The of date is . date is generated from by fixing the value of the facet equal to "P1D".

Lexical representation

The lexical representation for date is the reduced (right truncated) lexical representation for : CCYY-MM-DD. 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 "-" is allowed.

For example, to indicate May the 31st, 1999, one would write: 1999-05-31. See also .

Canonical representation

The canonical representation for date is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal Time (UTC) and be indicated by a "Z".

Constraining facets month

month represents a that starts at midnight on the first day of the month and lasts until the midnight that ends the last day of the month. The of month 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. The of month is . month is generated from by fixing the value of the facet equal to "P1M".

Lexical representation

The lexical representation for month is the reduced (right truncated) lexical representation for : CCYY-MM. 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 "-" is allowed.

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

Canonical representation

The canonical representation for month is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal Time (UTC) and be indicated by a "Z".

Constraining facets year

year represents a that starts at the midnight that starts the first day of the year and ends at the midnight that ends the last day of the year. The of year 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. The of year is . year is generated from by fixing the value of the facet equal to "P1Y".

Lexical representation

The lexical representation for year 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 "-" is allowed.

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

Canonical representation

The canonical representation for year is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal Time (UTC) and be indicated by a "Z".

Constraining facets century

century represents a that starts at the midnight that starts the first day of the century and ends at the midnight that ends that last day of the century. The of century is the set of Gregorian calendar centuries as defined in § 5.2.1 of . Specifically, it is a set of one-century long, non-periodic instances e.g. literal 19 to represent the whole of the 20th century. The of century is . century is generated from by fixing the value of the facet equal to "P100Y".

Lexical representation

The lexical representation for century is the reduced (right truncated) lexical representation for : CC. 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 "-" is allowed.

For example, to indicate the 20th century, one would write: 19. See also .

Canonical representation

The canonical representation for century is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal Time (UTC) and be indicated by a "Z".

Constraining facets recurringDate

recurringDate is a 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 recurringDate is the set of calendar dates, as defined in § 3 of . Specifically, it is a set of one-day long, annually periodic instances. The of recurringDate is . recurringDate is generated from by fixing the value of the facet equal to "P1D" and the value of the facet to "P1Y" (one year).

Lexical representation

The lexical representation for recurringDate is the left truncated lexical representation for : --MM-DD. No other formats are allowed. See also .

Canonical representation

The canonical representation for recurringDate is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal Time (UTC) and be indicated by a "Z".

Constraining facets recurringDay

recurringDay is a 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 recurringDay 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. The of recurringDay is . recurringDay is generated from by fixing the value of the facet equal to "P1D" and the value of the facet to "P1M".

Lexical representation

The lexical representation for recurringDay is the left truncated lexical representation for : ---DD . No other formats are allowed. See also .

Canonical representation

The canonical representation for recurringDay is defined by prohibiting certain options from the . Specifically, the preceding optional "+" sign is prohibited and the time zone must be Coordinated Universal Time (UTC) and be indicated by a "Z".

Constraining facets 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 absent are taken to have the null value.

Throughout the following sections, the &i-value; of an attribute information item means a string composed of, in order, the &i-ccode; of each character information item in the &i-attrChildren; of that attribute information item.

For more information on the notion of datatype (schema) components, see Schema Component Details of .

Readers whose primary interest is in the XML representation of datatype definitions might wish to skip this section on the first reading, concentrating instead on .

Datatype definition

Datatype 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 datatype definition schema component has the following properties:

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

Datatypes are identified by their and . Except for anonymous datatypes (those with no ), datatype definitions be uniquely identified within an 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 then is true and is finite if one of or and one of or are among , otherwise is false and is countably infinite, and are inherited from .

If is then is true and is finite if or both of and are among , otherwise is false and is countably infinite, and are false.

If is then is true if every member of is and all members of share a common ancestor and is false otherwise, is finite if the of every member of is finite and is countably infinite otherwise, is true if every member of is and all members of share a common ancestor and is false otherwise, are true if every member of is and is false otherwise.

applicable facets

The s which are allowed to be members of are dependent on as specified in the following table:

list of atomic

If is , then the of   be or .

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 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 .

Constraining facets

This section provides the details of each component.

s provide for:

Constraining the of a datatype by specifying optional properties which serve to semantically characterize the values in the .

Facet Valid

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

the value is facet-valid with respect to the particular as specified below.

length

provides for:

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

A . A . Optional. An annotation.

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

length and minLength or maxLength

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

Length Valid

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

if the is then

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

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

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

minLength

provides for:

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

A . A . Optional. An annotation.

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

minLength <= maxLength

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

minLength Valid

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

if the is then

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

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

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

maxLength

provides for:

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

A . A . Optional. An annotation.

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

maxLength Valid

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

if the is then

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

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

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

pattern

provides for:

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

A . Optional. An annotation. pattern valid

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

the value is among the set of values denoted by literals which are among the set of strings denoted by the specified in .

enumeration

provides for:

Constraining a to a specified set of values.

A set of values from the of the . Optional. An annotation. enumeration valid

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

the value be one of the values specified in .

whiteSpace

provides for:

Constraining a according to the white space normalization rules.

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 .

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

maxInclusive

provides for:

Constraining a to values with a specific inclusive .

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 .

minInclusive <= maxInclusive

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

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 ;

maxExclusive

provides for:

Constraining a to values with a specific exclusive .

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 .

maxInclusive and maxExclusive

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

minExclusive <= maxExclusive

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

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 ;

minExclusive

provides for:

Constraining a to values with a specific exclusive .

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 .

minInclusive and minExclusive

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

minExclusive Valid

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 ;

minInclusive

provides for:

Constraining a to values with a specific inclusive .

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 .

minInclusive Valid

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 ;

precision

provides for:

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

A . A . Optional. An annotation.

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

precision Valid

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

the number of decimal digits in the value is less than or equal to ;

scale

provides for:

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

A . A . Optional. An annotation.

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

scale less than or equal to precision

It is an for to be greater than .

scale Valid

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

the number of decimal digits in the fractional part of the value is less than or equal to ;

encoding

provides for:

Constraining the of datatypes from to a specified form.

One of {hex, base64}. A . Optional. An annotation.

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

There are no s associated with . determines the of datatypes from without constraining the .

duration

provides for:

Constraining a to values of a specific duration of time.

A . A . Optional. An annotation.

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

There are no s associated .

period

provides for:

Constraining a to values of a specific frequency of recurrence.

A . A . Optional. An annotation.

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

There are no s associated .

XML representation of datatype definitions

The sections below define correspondences between element information items and datatype definition components. All the element information items in the XML representation of a datatype definition are in the XML Schema namespace, that is their namespace URI is http://www.w3.org/2000/10/XMLSchema.

Throughout the following sections, the &i-value; of an attribute information item or the &i-children; of an element information item means a string composed of, in order, the &i-ccode; of each character information item in the &i-attrChildren; of that attribute information item or in the &i-children; of that element information item respectively.

XML representation of datatype definitions

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 value of the name &i-attribute;, if present, otherwise null The 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 value of of The union of the set of facet components corresponding to the facet &i-children;. Either the base &i-attribute; or the simpleType &i-children;, whichever is present. base attribute or simpleType child

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

One datatype can be from another datatype by restricting its and, consequently, its . Restriction of the is accomplished through the specification of values for one or more s.

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 .

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.

]]>

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

Derivation by list list The value of the itemType &i-attribute; itemType attribute or simpleType child

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

A datatype must be from an or a datatype, known as the of the datatype. This yields a datatype whose is composed of finite 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.

]]>

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 the above s, the unit of length is measured in number of list items.

Derivation by union union The type definitions resolved to by the items in the value of the memberTypes &i-attribute;, if any, in order, followed by the type definitions corresponding to the simpleType &i-children;, if any, in order. memberTypes attribute or simpleType children

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

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

An example, taken from a typical display oriented text markup language, 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

]]>

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

Constraining facets

This section discusses the details of the XML Representation for specifying s in a datatype definition.

length

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 value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

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.

]]> minLength

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 value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

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).

]]> maxLength

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 value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

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.

]]> pattern

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

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 .

]]> enumeration

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

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 ]]> whiteSpace

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 value of the . The value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

The following example is the datatype definition for the    datatype.

]]> maxInclusive

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 value of the . The value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

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

]]> maxExclusive

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 value of the . The value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

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').

minInclusive

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 value of the . The value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

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

]]> minExclusive

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 value of the . The value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

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').

precision

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 value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

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).

]]> scale

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 value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

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 .

]]> encoding

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

The value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

The following example is a datatype definition for a datatype whose is the set of binary streams of length 4 octets (32 bits) and whose is the set of base64 encodings of such binary streams. This datatype definition would appear in a schema authored by an "end-user" and shows how to define a datatype by specifying multiple s.

]]> duration

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 value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

Suppose an health insurance company wanted to define the length of a hospital stay permitted for the birth of a baby as two days. They might want to define a datatype as below.

]]> period

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 value of the value &i-attribute; The value of the fixed &i-attribute;, if present, otherwise false The annotation corresponding to the element information item in the &i-children;, if present, otherwise null

Suppose we wanted to define a day of the week i.e. a duration of one day that recurs every 7 days. This could be done as follows:

]]> 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 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 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 optimised 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 Fundamental Facets

The following table shows the values of the fundamental facets for each datatype.

Constraining Facets

The s are listed below with all the and datatypes that they apply to.

ISO 8601 Date and Time Formats ISO 8601 Conventions

The two datatypes described above, , , and the five datatypes , , , , and use lexical formats inspired by . 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 Gregorian calendar and times and representations of periods of time". The 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 digits. For and types derived from it, 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 23.

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 is allowed only in the case of leap seconds.

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 and

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 . By truncating the date information we represent an instant of time that recurs every day. Similarly, the and datatypes use left-truncated formats 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 , , and .

Deviations from ISO 8601 Formats Sign Allowed

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

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 datatypes from it. This follows .

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.

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

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.

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 .

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.

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

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.

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).

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).

A character group is either , a , or a .

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.

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).

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

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 Unicode code points in a specified range.

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 ; and

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

A   also be written in the form s-e, identifying the set that contains all XML characters with Unicode 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 include the s, the s, and the s.

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 .

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)
\\ \
\| |
\. .
\- -
\^ ^
\? ?
\* *
\+ +
\{ {
\} }
\( (
\) )
\[ [
\] ]

defines a number of character properties 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}]).

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 the Unicode Standard 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 of the Unicode Standard.

The syntax \p{X} is the same as that used in .

The following table specifies the main character properties (for more information, see Chapter 4 of ).

Category Property Meaning
Letters L All Letters
Lu Uppercase
Ll Lowercase
Lt Titlecase
Lm Modifier
Lo Other
 
Marks M All Marks
Mn Non-Spacing
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 (can behave like Ps or Pe depending on usage)
Pf Final quote (can 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

The properties mentioned exclude the Cs property described in Chapter 4 of . 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 compliment of this set is specified with the block escape \P{IsX}. ([\P{IsX}] = [^\p{IsX}]).

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 the Unicode Standard 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.

The syntax \p{IsX} is the same as that used in .

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:

Character sequence Equivalent
. [^\n\r]
\s [#x20\t\n\r]
\S [^\s]
\i [\p{L}\p{Nl}:_]
\I [^\i]
\c the set of characters matched by NameChar
\C [^\c]
\d \p{Nd}
\D [^\d]
\w [#x0000-#x10FFFF]-[\p{P}\p{S}\p{C}] (all characters except the set of "punctuation", "separator" and "control" characters)
\W [^\w]

The language defined here does not attempt to provide a general solution to "regular expressions" over strings. 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.

Future versions of this specification might allow non-significant white space embedded within a . The XML Schema Working Group welcomes feedback from implementors and schema authors on the advisability of including such white space. References Normative 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 Information Set (public WD) Available at: http://www.w3.org/TR/xml-infoset World Wide Web Consortium. Extensible Markup Language (XML) 1.0, Second Edition. Available at: &xmlspec; XML Schema Part 1: Structures. Available at: &xsdl; XML Schema Requirements. Available at: http://www.w3.org/TR/NOTE-xml-schema-req 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 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 Standard, Version 3.0. Reading, Mass.: Addison-Wesley Developers Press, 2000. ISBN 0-201-61633-5. Non-normative ISO (International Organization for Standardization). ISO/IEC 10646-1993 (E). Information technology --- Universal Multiple-Octet Coded Character Set (UCS) --- Part 1: Architecture and Basic Multilingual Plane. [Geneva]: International Organization for Standardization, 1993 (plus amendments AM 1 through AM 7). ISO (International Organization for Standardization). ISO/IEC 10646-1:2000. Information technology --- Universal Multiple-Octet Coded Character Set (UCS) --- Part 1: Architecture and Basic Multilingual Plane. [Geneva]: International Organization for Standardization, 2000. The Unicode Consortium. The Unicode Standard, Version 2.0. Reading, Mass.: Addison-Wesley Developers Press, 1996. The Unicode Consortium. The Unicode Character Database. Available at: http://www.unicode.org/Public/3.0-Update/UnicodeCharacterDatabase-3.0.0.html 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 The Perl Programming Language, Version 5.6. See http://www.perl.com/language/misc/ann58/index.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 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). 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/rdf-schema/ World Wide Web Consortium. Extensible Stylesheet Language (XSL). Available at: http://www.w3.org/TR/xsl/ World Wide Web Consortium. XML Pointer Language (XPointer) . Available at: http://www.w3.org/TR/WD-xptr Martin J. Dürst and François Yergeau, eds. Character Model for the World Wide Web. World Wide Web Consortium Working Draft. 1999 Available at: http://www.w3.org/TR/1999/WD-charmod-19991129/ 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 draft:

David Fallside, IBM Scott Lawrence, Agranat Systems Andrew Layman, Microsoft Eve L. Maler, Sun Microsystems

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 members of the XML Schema Working Group are:

Jim Barnette Defense Information Systems Agency (DISA) David Beech Oracle Corp. 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 Mike Cokus MITRE Dan Connolly W3C staff contact Roger L. Costello MITRE Ugo Corda Xerox Haavard Danielson Progress Software David Ezell Hewlett Packard Company David Fallside IBM Matthew Fuchs Commerce One Andrew Goodchild Distributed Systems Technology Centre (DSTC Pty Ltd) Paul Grosso ArborText, Inc Martin Gudgin DevelopMentor Dave Hollander Contivo co-chair Mary Holstege Calico Commerce Jane Hunter Distributed Systems Technology Centre (DSTC Pty Ltd) Rick Jelliffe Academia Sinica Andrew Layman Microsoft Dmitry Lenkov Hewlett Packard Company Ashok Malhotra IBM Murray Maloney Muzmo Communication, acting for Commerce One John McCarthy Lawrence Berkeley National Laboratory Noah Mendelsohn Lotus Development Corporation Don Mullen TIBCO Extensibility Alex Milowski Lexica LLC Frank Olken Lawrence Berkeley National Laboratory Dave Peterson Graphic Communications Association Jonathan Robie Software AG Lew Shannon NCR C. M. Sperberg-McQueen W3C co-chair Bob Streich Calico Commerce Henry S. Thompson University of Edinburgh Matt Timmermans Microstar Jim Trezzo Oracle Corp. Mark Tucker Health Level Seven Asir S. Vedamuthu webMethods, Inc Priscilla Walmsley XMLSolutions Norm Walsh Sun Microsystems Aki Yoshida SAP AG

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 Gabe Beged-Dov Rogue Wave Software Greg Bumgardner Rogue Wave Software Dean Burson Lotus Development Corporation 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) Murata Makoto Xerox Eve Maler Sun Microsystems Chris Olds Wall Data Shriram Revankar Xerox Mark Reinhold Sun Microsystems John C. Schneider MITRE William Shea Merrill Lynch Ralph Swick W3C Tony Stewart Rivcom Steph Tryphonas Microstar Revisions from Previous Draft