ISO/IEC 19757-5:2011

INTERNATIONAL ISO/IEC
STANDARD 19757-5
First edition
2011-10-01


Information technology — Document
Schema Definition Languages (DSDL) —
Part 5:
Extensible Datatypes
Technologies de l'information — Langages de définition de schéma de
documents (DSDL) —
Partie 5: Types de données extensibles




Reference number
ISO/IEC 19757-5:2011(E)
©
ISO/IEC 2011

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ISO/IEC 19757-5:2011(E)

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ISO/IEC 19757-5:2011(E)
Contents Page
Foreword . iv
Introduction . v
1  Scope . 1
2  Normative references . 1
3  Terms and definitions . 2
4  Extensible Datatypes schema overview . 2
5  Common constructs . 3
5.1  Common types . 3
5.2  Common attributes . 4
5.3  Extension elements . 4
5.4  Versioning and compatibility . 5
6  Simplification . 5
6.1  Include elements . 5
6.2  Same-named datatypes . 6
7  Document element . 7
8  Top-level elements . 7
8.1  div element . 8
8.2  Top-level extension elements . 8
9  Datatype definition . 8
9.1  Named datatypes . 8
9.2  Anonymous datatypes . 8
9.3  Whitespace processing . 9
9.4  Mechanisms for defining datatypes . 9
Annex A (normative) RELAX NG schema for Extensible Datatypes documents . 16
Bibliography . 18

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ISO/IEC 19757-5:2011(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
ISO/IEC 19757-5 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 34, Document description and processing languages.
ISO/IEC 19757 consists of the following parts, under the general title Information technology — Document
Schema Definition Languages (DSDL):
 Part 1: Overview
 Part 2: Regular-grammar-based validation — RELAX NG
 Part 3: Rule-based validation — Schematron
 Part 4: Namespace-based Validation Dispatching Language (NVDL)
 Part 5: Extensible Datatypes
 Part 7: Character Repertoire Description Language (CREPDL)
 Part 8: Document Semantics Renaming Language (DSRL)
 Part 9: Namespace and datatype declaration in Document Type Definitions (DTDs)
 Part 11: Schema Association
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ISO/IEC 19757-5:2011(E)
Introduction
This part of ISO/IEC 19757 specifies a powerful, XML-based language which enables users to create and
extend their own libraries of datatypes using straightfoward declarative XML constructs. Such libraries are
well-suited to being used in pipelining validation processes in conjunction with other XML schema languages.
[1]
Unlike W3C Schema , ISO/IEC 19757-2:2008 (RELAX NG) does not itself provide a declarative mechanism
for users to define their own datatypes. If they are not satisfied with the two built-in types of string and
token, RELAX NG users have had either to use a pre-written library bundled with their validator, or to
program a datatype library using that validator's API. Such programmed datatype libraries are hard to
construct for non-programmer users, and built-in datatype libraries are often insufficient for users' needs.

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INTERNATIONAL STANDARD ISO/IEC 19757-5:2011(E)

Information technology — Document Schema Definition
Languages (DSDL) —
Part 5:
Extensible Datatypes
1 Scope
This part of ISO/IEC 19757 specifies an XML language that allows users to create and extend datatype
libraries for their own purposes. The datatype definitions in these libraries can be used by XML validators and
other tools to validate content and make comparisons between values.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
IETF RFC 3023, XML Media Types, Internet Standards Track Specification, January
2001, http://www.ietf.org/rfc/rfc3023.txt
IETF RFC 3987, Internationalized Resource Identifiers (IRIs), Internet Standards Track Specification, January
2005, http://www.ietf.org/rfc/rfc3987.txt
ISO/IEC 19757-2:2008, Information technology — Document Schema Definition Language (DSDL) — Part 2:
Regular-grammar-based validation — RELAX NG
W3C XML, Extensible Markup Language (XML) 1.0 (Fourth Edition), W3C Recommendation, 16 August 2006,
edited in place 29 September 2006, http://www.w3.org/TR/2006/REC-xml-20060816
W3C XML Names, Namespaces in XML 1.0 (Third Edition), W3C Recommendation, 8 December
2009, http://www.w3.org/TR/2009/REC-xml-names-20091208/
W3C XPath 2.0, XML Path Language (XPath) 2.0, W3C Recommendation, 23 January
2007, http://www.w3.org/TR/2007/REC-xpath20-20070123/
W3C XPath 2.0 Functions, XQuery 1.0 and XPath 2.0 Functions and Operators, W3C Recommendation, 23
January 2007, http://www.w3.org/TR/2007/REC-xpath-functions-20070123/
W3C XSLT 2.0, XSL Transformations (XSLT) Version 2.0, W3C Recommendation, 23 January
2007, http://www.w3.org/TR/2007/REC-xslt20-20070123/
W3C XLink 1.0, XML Linking Language (XLink) Version 1.0, W3C Recommendation, 27 June
2001, http://www.w3.org/TR/2001/REC-xlink-20010627/
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ISO/IEC 19757-5:2011(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
candidate value
some character data in an XML document that is to have its datatype tested
3.2
datatype
named property of sequences of character data that validate against datatype definitions as described by this
part of ISO/IEC 19757
3.3
datatype definition
formal specification of constraints upon XML character data for the datatype being defined
3.4
datatype library
collection of datatype definitions that share the same XML Namespace
3.5
Extensible Datatypes document
XML document which is valid to the normative schema presented in this part of ISO/IEC 19757, and which
conforms to its provisions
3.6
forwards-compatible mode
operating mode in which an implementation ignores language constructs which are labelled as having a
version later than that understood by the implementation, unless they are explicitly labelled as requiring
processing
3.7
implementation
Extensible Datatypes implementation that conforms to this part of ISO/IEC 19757
3.8
extended implementation
implementation that conforms to this part of ISO/IEC 19757, and which provides additional functionality
provided by the extension mechanisms of Extensible Datatypes
4 Extensible Datatypes schema overview
The schema for Extensible Datatypes is interspersed as fragments within the narrative text of this part of
ISO/IEC 19757 and appears rendered against a grey background. The schema language used is the compact
syntax of RELAX NG, as defined by Annex C of ISO/IEC 29500:2008.
Concatenating the schema fragments in this part of ISO/IEC 19757 gives a RELAX NG schema that
normatively defines the grammar of Extensible Datatypes. The consolidated schema is shown in Annex A.
NOTE 1 Throughout, as per ISO/IEC 19757-2:2008, RELAX NG compact syntax keywords used as identifiers in the
schema are prefixed with the "\" character.
NOTE 2 The null Namespace is bound to the prefix "local" so that it can be referenced later in the schema.
 default namespace dt =
      "http://purl.oclc.org/dsdl/extensible-datatypes"
 namespace local = ""
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ISO/IEC 19757-5:2011(E)
Datatype libraries are defined in ISO/IEC 19757-2:2008 as being identified by an IRI, with each datatype
within a given datatype library being identified by a NCName. An Extensible Datatypes document presents
one or more such datatype libraries to implementations. Each datatype definition has a qualified name; the
Namespace IRI identifies the datatype library to which the datatype belongs, and the local part identifies the
name of the datatype within that datatype library.
5 Common constructs
5.1 Common types
5.1.1 XPath expressions
W3C XPath 2.0 expressions are used to bind values to variables or properties and to express tests in
conditions. Conforming implementations of Extensible Datatypes shall additionally implement the following
functions from W3C XSLT 2.0:
— document (W3C XSLT 2.0, section 16.1)
— format-number (W3C XSLT 2.0, section 16.4)
— function-available (W3C XSLT 2.0, section 18.1.1)
These functions shall be callable within implementations using unqualified function names.
NOTE The function-available function can be used to test for the availability of XPath extension functions for the
purposes of enhanced validation in extended implementations.
 XPath = text
The context node for evaluating XPath expressions in Extensible Datatypes is a text node that is the only child
of a root node, and whose value is the whitespace-normalized candidate value. The context position and
context size are both 1. The set of variable bindings are the in-scope variables, as defined at 9.4.1. The set of
namespace declarations that are in-scope for the expression are those that are in-scope for the element on
which the XPath is given.
5.1.2 Boolean values
Where a boolean value is to be specified, the literal strings "true" and "false" are used.
 boolean = "true" | "false"
5.1.3 Regular expressions
Regular expressions are defined in W3C XPath 2.0.
 regular-expression = text
5.1.4 Arbitrary content
Extensible Datatypes document are governed by an open schema which, for purposes of extensibility, allows
arbitrary content to occur at certain points. Such content can be any XML content other than elements or
attributes associated with the Extensible Datatypes XML Namespace.
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ISO/IEC 19757-5:2011(E)
anything =
 mixed {
  element * - dt:* {
   attribute * - dt:* { text }*,
   anything
  }*
 }
5.2 Common attributes
5.2.1 version attribute
The value of the version attribute specifies the version of Extensible Datatypes being used within the
element on which it occurs. The version described by this International Standard is "1.0"
5.2.2 ns attribute
The value of the ns attribute specifies the Namespace IRI of those datatypes defined within that element
whose name attribute does not include a prefix, thus determining the datatype library to which these datatypes
belong. This value shall be an IRI as defined by IETF RFC 3987.
 ns = attribute ns { text }
5.2.3 name attribute
The name attribute specifies the name of a datatype, parameter, variable or property. The value of a name
attribute is a qualified name. If no prefix is specified the Namespace IRI associated with the name depends on
the element on which the name attribute occurs. If the name attribute occurs on a datatype element, the
Namespace IRI is that given in the ns attribute of the datatype element or its nearest ancestor element that
has a ns attribute, if there is one, or no Namespace IRI if there is not. Otherwise, the unprefixed name has no
Namespace IRI.
NOTE Names conform to the text pattern defined by ISO/IEC 29500-2:2008 and so are less constrained that names
in some other schema specifications.
 name = attribute name { text }
5.2.4 Extension attributes
Extension attributes are attributes in any non-null Namespace other than the Extensible Datatypes
namespace. They can occur on any Extensible Datatypes element. The presence of such attributes shall not
change the behaviour of the Extensible Datatypes elements defined in this part of ISO/IEC 19757: an
implementation shall return the same result whether extension attributes are processed or not.
 extension-attribute = attribute * - (local:* | dt:*) { text }
5.3 Extension elements
Extension elements are elements in any Namespace other than the Extensible Datatypes Namespace. They
may be processed by extended implementations. There are three classes of extension element:
— top-level extension elements, which occur as children of the document element or div elements
— definition extension elements, which occur as children of datatype elements
— binding extension elements, which occur wherever a value can be bound (for example, to a variable)
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ISO/IEC 19757-5:2011(E)
 extension-element =
  element * - dt:* {
   must-implement?,
   attribute * - ( dt:* | must-implement) { text }*,
   anything
  }
5.4 Versioning and compatibility
An Extensible Datatypes element is processed in forwards-compatible mode if it, or its nearest ancestor that
has a version attribute, has a version attribute with a value greater than "1.0". When an element in the
Extensible Datatypes namespace that is not described by this part of ISO/IEC 19757 is processed in forwards-
compatible mode it, its attributes and its descendants shall be ignored unless it has a must-implement
attribute with the value true, in which case an implementation shall halt and emit an error message.
 must-implement = attribute must-implement { boolean }
6 Simplification
Before it is applied for validation, an Extensible Datatypes document is simplified into a single logical unit by
processing any include elements and resolving any multiple occurrences of same-named data types into a
single definition.
6.1 Include elements
include elements reference other Extensible Datatypes datatype libraries. They import datatypes from these
libraries or redefine them using definitions in the host document.
 \include =
    element include {
    ns?,
    attribute href { text },
    extension-attribute*,
    top-level-element*
    }
The ns attribute on include is used to override the namespace of imported datatypes as defined using the
ns attribute in the document being included.
The href attribute specifies an IRI reference. This IRI reference is first transformed by escaping disallowed
characters as specified in Section 5.4 of W3C XLink 1.0. If it is not absolute, the IRI reference is resolved into
an absolute form as described in section 5 of IETF RFC 3987 using the base IRI of the include element.
The value of the href attribute is thus used to create a datatypes element, as follows. The IRI reference
consists of the IRI itself and an optional fragment identifier. The resource identified by the IRI is retrieved. The
result is a MIME entity: a sequence of octets labeled with a MIME media type. The media type determines
how an element is constructed from the MIME entity and optional fragment identifier. When the media type is
application/xml or text/xml, the MIME entity shall be parsed as an XML document in accordance with
the applicable RFC (at the time of writing [RFC 3023]) and an element, which shall be a datatypes element
in the Extensible Datatypes namespace, constructed from the result of the parse. In particular, the charset
parameter shall be handled as specified by the RFC. This specification does not define the handling of media
types other than application/xml and text/xml. The href attribute shall not include a fragment identifier
unless the registration of the media type of the resource identified by the attribute defines the interpretation of
fragment identifiers for that media type.
NOTE [RFC 3023] does not define the interpretation of fragment identifiers for application/xml or text/xml.
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ISO/IEC 19757-5:2011(E)
The datatypes element thus determined by the href attribute value is processed such that its include
elements are resolved. It is not permitted for this to result in a loop. In other words, the datatypes element
shall not require the dereferencing of an include element with an href attribute with the same value. This
results in a number of datatype definitions. If the include element contains any datatype elements then for
every datatype defined within the include element, there shall be a datatype definition in the referenced
library with the same name. All datatype definitions from the referenced datatype library with the same name
as a datatype definition within the include element are ignored.
The include element is treated the same as a div element with the same attributes, except for the href
attribute. The first child of the equivalent div element is another div element whose attributes and children
are the same as those on the referenced datatypes element, with the exception of those that are overridden
by definitions within the include element as defined above. The remaining children of the equivalent div are
the children of the include element.
6.2 Same-named datatypes
 \combine = attribute combine { "choice" | "all" }
If, as a result of an inclusion (as described in section 6.1) or otherwise, two or more datatype definitions have
the same expanded qualified name, they are combined together. For any name, there shall not be more than
one datatype element with that name that does not have a combine attribute. For any name, if there is a
datatype element with that name that has a combine attribute with the value "choice", there shall be no
datatype element with that name that has a combine attribute with the value "all". Thus, for any name, if
there is more than one datatype element with that name, then there is a unique value for the combine
attribute for that name. After determining this unique value, the combine attributes are removed. If both
datatype elements have a param element with the same name, those param elements shall specify the
same type and value. Definitions are combined until there is exactly one datatype element for each name.
EXAMPLE The following two definitions for the a colour specification
 
  #([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})
  
  
  
 

 
  #([0-9A-Fa-f])([0-9A-Fa-f])([0-9A-Fa-f])
  
  
  
 
are, by the combination process, combined into a single definition equivalent to:
 
  
   
    #([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})([0-9A-Fa-f]{2})
    
    
    
   
   
    #([0-9A-Fa-f])([0-9A-Fa-f])([0-9A-Fa-f])
    
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If the choice attribute specified "all" then all definitions apply, so the two definitions
 
  [A-Z]{3}
 

 
  [A-Z]{3}
  
  
 
are, by the combination process, combined into a single definition equivalent to:
 
  
   
    [A-Z]{3}
   
   
    [A-Z]{3}
    
    
   
  
 
7 Document element
The document element of an Extensible Datatypes document is datatypes. It has a required version
attribute (see 5.2.1) and an optional ns attribute (see 5.2.2).
 start = \datatypes

 \datatypes =
   element datatypes {
    version, ns?, extension-attribute*, top-level-element*
   }

 version = attribute version { "1.0" }
8 Top-level elements
Top-level elements occur as children of the document element.
 top-level-element = \include | named-datatype | \div | extension-top-level-element
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8.1 div element
div elements are used to partition a datatype library.
NOTE Their use is equivalent to that of div elements in ISO/IEC 19757-2:2008.
 \div =
  element div {
   ns?, version?, extension-attribute*, top-level-element*
  }
8.2 Top-level extension elements
Top-level extension elements can be used to hold content that is used within the datatype library (such as
code lists used to test enumerated values), documentation, or other information that is used by extended
implementations. For example, an extension top-level element can be used by an extended implementation to
define extension functions (using XSLT, for example) that can be used in the XPath expressions used within
the datatype library.
 extension-top-level-element = extension-element
Top-level extension elements are treated in the same way as other extension elements (see 5.3).
9 Datatype definition
Datatype definitions within a datatype library can be either named or anonymous.
9.1 Named datatypes
Named datatypes definitions for a datatype library are specified at the top level of the datatype library
document using datatype elements. Each named datatype definition has a name specified in the name
attribute that uniquely identifies it (see 5.2.3).
 named-datatype =
  element datatype {
   name,
   ns?,
   preprocess?,
   combine?,
   extension-attribute*,
   param*,
   datatype-definition-element*
  }
9.2 Anonymous datatypes
Anonymous datatypes (see 9.4.1.5) are used to define datatypes that cannot be referred to by name.
 anonymous-datatype =
  element datatype {
   preprocess?, extension-attribute*, datatype-definition-element*
  }
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9.3 Whitespace processing
The normalize-whitespace attribute determines how a candidate value is whitespace-normalized prior to
testing against the datatype definition elements. If normalize-whitespace has the value preserve no
whitespace normalization is carried out. If normalize-whitespace has the value replace all whitespace
characters (spaces, tabs, newlines and carriage returns) are replaced by a single space character (U+0020).
Otherwise (if normalize-whitespace has the value collapse or is not specified), leading and trailing
whitespace is removed and all internal sequences of whitespace characters are replaced by a single space
character.
 preprocess =
  attribute normalize-whitespace { "preserve" | "replace" | "collapse" }
9.4 Mechanisms for defining datatypes
A datatype definition consists of a number of elements that test values and define variables and properties. If
a candidate value obeys the constraints specified by these elements, then it is a valid value for the datatype.
 datatype-definition-element =
    property
    | variable
    | regex
    | \list
    | condition
    | valid
    | except
    | choice
    | all
    | extension-definition-element
9.4.1 Properties, variables and parameters
param, property and variable declare variables, and are thus known as variable-binding elements. The
name of the variable is specified in the name attribute of the variable-binding element (see 5.2.3). The scope
of a variable binding is the following siblings of the variable binding element and their descendants.
NOTE A variable or property specified within a choice is not available outside that choice.
9.4.1.1 Properties
The property element specifies a property of a candidate value. When a candidate value is validated against
a datatype, it is associated with a name/type/value triple for each property.
...