ISO/IEC 13250-4:2009

Information technology — Topic Maps — Part 4: Canonicalization

ISO/IEC 13250-4:2009 defines a format known as Canonical XTM, or CXTM for short. The format is an XML format, and has the property that it guarantees that two equivalent Topic Maps Data Model instances (ISO/IEC 13250-2) will always produce byte-by-byte identical serializations, and that non-equivalent instances will always produce different serializations. CXTM thus enables direct comparison of two topic maps to determine equality by comparison of their canonical serializations. The purpose of CXTM is to allow the creation of test suites for various Topic Maps-related technologies that are easily portable between different Topic Maps implementations, so long as these support CXTM. CXTM is not intended to be used for the interchange of topic maps, although this is possible. The standard format for interchange of topic maps is XTM (ISO/IEC 13250-3). ISO/IEC 13250-4:2009 specifies how CXTM files are produced from topic maps by means of a transformation from the Topic Maps Data Model (ISO/IEC 13250-2) to the XML Infoset.

Technologies de l'information — Plans relatifs à des sujets — Partie 4: Canonicalisation

General Information

• Status: Published
• Publication Date: 17-Feb-2009
• ICS: 35.240.30 - IT applications in information, documentation and publishing
• Technical Committee: ISO/IEC JTC 1/SC 34 - Document description and processing languages
• Drafting Committee: ISO/IEC JTC 1/SC 34 - Document description and processing languages
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 10-Jan-2020

Relations

• Revises: ISO/IEC 13250:2003 - Information technology — SGML applications — Topic maps
• Effective Date: 26-Nov-2021

Standards Content (Sample)

INTERNATIONAL ISO/IEC
STANDARD 13250-4
First edition
2009-03-01


Information technology — Topic Maps —
Part 4:
Canonicalization
Technologies de l'information — Plans relatifs à des sujets —
Partie 4: Canonicalisation




Reference number
ISO/IEC 13250-4:2009(E)
©
ISO/IEC 2009

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ISO/IEC 13250-4:2009(E)
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ISO/IEC 13250-4:2009(E)
Page
Contents
Foreword. iv
Introduction. v
1 Scope. 1
2 Normative references. 1
3 Canonicalization. 1
3.1 Introduction. 1
3.2 Notational conventions. 2
3.3 CXTM document information item. 2
3.4 Constructing a representation of a topic map item. 2
3.5 Constructing a representation of a topic item. 2
3.6 Constructing a representation of the topic name item. 3
3.7 Constructing a representation of a variant item. 3
3.8 Constructing a representation of an occurrence item. 3
3.9 Constructing a representation of an association item. 4
3.10 Constructing a representation of the association role item. 4
3.11 Constructing a representation of the [reifier] property. 4
3.12 Constructing a representation of the [scope] property. 5
3.13 Constructing a representation of the [item identifiers] property. 5
3.14 Constructing a representation of the [datatype] property. 5
3.15 Constructing a representation of the [type] property. 5
3.16 Constructing a representation of the [value] property. 5
3.17 Constructing a representation of locator values. 6
3.18 Normalizing locator values. 6
3.19 Constructing the number attribute. 6
3.20 Encoding of string properties. 7
3.21 Encoding of positional values. 7
3.22 Default property values for element information items. 7
3.23 Default property values for attribute information items. 7
4 Canonical sort order. 7
4.1 Introduction. 7
4.2 Information type and basic type sort order. 7
4.3 Comparison of strings. 8
4.4 Comparison of sets. 8
4.5 Comparison order for locators. 8
4.6 Canonical sort order for topic items. 8
4.7 Canonical sort order for topic name items. 8
4.8 Canonical sort order for variant items. 8
4.9 Canonical sort order for occurrence items. 8
4.10 Canonical sort order for association items. 9
4.11 Canonical sort order for association role items. 9
Annex A (informative) RELAX-NG schema for CXTM. 10
Bibliography. 12
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ISO/IEC 13250-4:2009(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 13250-4 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 34, Document description and processing languages.
ISO/IEC 13250 consists of the following parts, under the general title Information technology — Topic Maps:
 Part 2: Data model
 Part 3: XML syntax
 Part 4: Canonicalization
The following parts are under preparation.
 Part 1: Overview and basic concepts
 Part 5: Reference model
 Part 6: Compact syntax

 Part 7: Graphical notation
iv © ISO/IEC 2009 – All rights reserved

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ISO/IEC 13250-4:2009(E)
Introduction
This part of ISO/IEC 13250 defines a format known as Canonical XTM, or CXTM for short. The format is an XML format,
and has the property that it guarantees that two equivalent Topic Maps Data Model instances (ISO/IEC 13250-2) will
always produce byte-by-byte identical serializations, and that non-equivalent instances will always produce different
serializations. CXTM thus enables direct comparison of two topic maps to determine equality by comparison of their
canonical serializations.
The purpose of CXTM is to allow the creation of test suites for various Topic Maps-related technologies that are easily
portable between different Topic Maps implementations, so long as these support CXTM.
CXTM is not intended to be used for the interchange of topic maps, although this is possible. The standard format
for interchange of topic maps is XTM (ISO/IEC 13250-3).
© ISO/IEC 2009 – All rights reserved
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INTERNATIONAL STANDARD                                     ISO/IEC 13250-4:2009(E)
Information technology — Topic Maps —
Part 4:
Canonicalization
1 Scope
This part of ISO/IEC 13250 defines the CXTM format, and specifies how CXTM files are produced from topic maps

by means of a transformation from the Topic Maps Data Model (ISO/IEC 13250-2) to the XML Infoset [XML Infoset].
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.
NOTE Each of the following documents has a unique identifier that is used to cite the document in the text. The unique
identifier consists of the part of the reference up to the first comma.
ISO/IEC 10646, Information technology — Universal Multiple-Octet Coded Character Set (UCS)
Unicode, The Unicode Standard, Version 5.0.0, The Unicode Consortium, Reading, Massachusetts, USA, Addison-
Wesley Developer's Press, 2007, ISBN 0-321-48091-0, http://www.unicode.org/versions/Unicode5.0.0/
RFC 3986, Uniform Resource Identifier (URI): Generic Syntax, Internet Standards Track Specification, January
2005, http://www.ietf.org/rfc/rfc3986.txt
XML-C14N, Canonical XML, Version 1.0, World Wide Web Consortium, 15 March 2001, available at

XML Infoset, XML Information Set (Second Edition), World Wide Web Consortium, 4 February 2004, available at

ISO/IEC 13250-2, Information technology — Topic Maps — Part 2: Data model
XMLSCHEMA-2, XML Schema Part 2: Datatypes Second Edition, World Wide Web Consortium, 28 October 2004,
available at
3 Canonicalization
3.1 Introduction
The canonicalization process takes two parameters: a topic map item (that is, an instance of the Topic Maps Data
Model, defined in ISO/IEC 13250-2) and a base locator. The process produces a canonicalization of the topic map,
with all locators in the topic map rewritten to be relative to the given base locator. The purpose of the base locator
is to allow references to the local filesystem to be stripped out, thus making CXTM test cases portable between
different systems.
Canonicalization is performed in three steps:
1. A document information item representing the CXTM document is produced from the topic map item as
described in 3.3.
2. For each element information item that is a descendant of the document information item from the previous
step, the following operations are performed:
— A character information item is added to the [[children]] property of the information item in the element's
[[parent]] property immediately after the element itself. The character information item's [[character
code]] property is set to #x0A.
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ISO/IEC 13250-4:2009(E)
— If the element's [[local name]] property is set to "topicMap", "topic", "name", "variant", "occurrence",
"association", "role", "scope", "itemIdentifiers", "subjectLocators", or "subjectIdentifiers", a character
information item is added to the [[children]] property of the element as the first element. The character
information item's [[character code]] property is set to #x0A.
3. The document information item is serialized to a Canonical XML representation as described in [XML-C14N].
3.2 Notational conventions
Information item properties from [W3C XML-Infoset] are referred to using [[property name]], in order to distinguish
them from properties from ISO/IEC 13250-2.
3.3 CXTM document information item
There is exactly one CXTM document information item in the XML Infoset generated by the canonicalization of the
topic map item.
The CXTM document information item has the following properties:
1. [[children]] A list containing only the representation of the topic map item
2. [[document element]] The element information item that represents the topic map item
3. [[notations]] The empty set
4. [[unparsed entities]] The empty set
5. [[base URI]] No value
6. [[standalone]] No value
7. [[version]] No value
8. [[all declarations processed]] False
3.4 Constructing a representation of a topic map item
A topic map item is represented by an element information item with the following properties:
1. [[local name]] The string "topicMap"
2. [[children]] A list of element information items in the following order:
1. A representation of the [item identifiers] property, if any
2. A representation of each topic item in the [topics] property of the topic map item in canonical sort order
3. A representation of each association item in the [associations] property of the topic map item in
canonical sort order
3. [[attributes]] A representation of the [reifier] property
3.5 Constructing a representation of a topic item
A topic item is represented by an element information item with the following properties:
1. [[local name]] The string "topic"
2. [[children]] A list of element information items in the following order:
1. If the value of [subject identifiers] property of the topic item is not the empty set, then an element
information item with the following properties:
1. [[local name]] The string "subjectIdentifiers"
2. [[children]] A representation of each locator in the [subject identifiers] property in canonical sort
order
3. [[attributes]] The empty set
2. If the value of the [subject locators] property of the topic item is not the empty set, then an element
information item with the following properties:
1. [[local name]] The string "subjectLocators"
2. [[children]] A representation of each locator in the [subject locators] property in canonical sort
order
3. [[attributes]] The empty set
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ISO/IEC 13250-4:2009(E)
3. A representation of the [item identifiers] property, if any
4. A representation of each of the topic name items of the [topic names] property in canonical sort order
5. A representation of each of the occurrence items of the [occurrences] property in canonical sort order
6. For each of the association role items of the [roles played] property in canonical sort order, an element
information item with the following properties
1. [[local name]] set to the string "rolePlayed"
2. [[children]] An empty list
3. [[attributes]] A set containing one attribute information item as follows:
1. [[local name]] set to the string "ref"
2. [[normalized value]] A sequence of character information items representing a string
value constructed by the concatenation of:
1. The string "association."
2. The position of the association item which is the value of the [parent] property
of the association role item, in the canonically sorted [associations] property of
the
...