ISO/IEC 19757-7:2020
(Main)Information technology — Document Schema Definition Languages (DSDL) — Part 7: Character Repertoire Description Language (CREPDL)
Information technology — Document Schema Definition Languages (DSDL) — Part 7: Character Repertoire Description Language (CREPDL)
This document specifies a Character Repertoire Description Language (CREPDL). A CREPDL schema describes a character repertoire. A stream of UCS code points can be validated against a CREPDL schema.
Technologies de l'information — Langages de définition de schéma de documents (DSDL) — Partie 7: Langage de description de répertoire de caractères (CREPDL)
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Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 19757-7
Second edition
2020-08
Information technology — Document
Schema Definition Languages
(DSDL) —
Part 7:
Character Repertoire Description
Language (CREPDL)
Technologies de l'information — Langages de définition de schéma de
documents (DSDL) —
Partie 7: Langage de description de répertoire de caractères
(CREPDL)
Reference number
©
ISO/IEC 2020
© ISO/IEC 2020
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ii © ISO/IEC 2020 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Notation . 2
5 Overview . 3
5.1 Basic constructs and compound constructs . 3
5.2 Characters and code points . 3
5.3 Grapheme clusters . 3
5.4 Kernel and Hull . 3
6 Syntax . 3
6.1 General . 3
6.2 RELAX NG schema . 4
6.3 NVDL script . 5
6.4 Regular Expressions . 5
7 Semantics . 5
7.1 General . 5
7.2 char . 6
7.3 union . 7
7.4 intersection . 7
7.5 difference . 7
7.6 ref . 8
7.7 repertoire . 8
8 Validation . 8
Annex A (informative) Differences of conformant processors .10
Annex B (informative) Example CREPDL schemas .11
Bibliography .15
© ISO/IEC 2020 – All rights reserved iii
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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for
the different types of document should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
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. Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www .iso .org/ patents) or the IEC
list of patent declarations received (see http:// patents .iec .ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT), see www .iso .org/
iso/ foreword .html.
This document was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 34, Document description and processing languages.
This second edition cancels and replaces the first edition (ISO/IEC 19757-7:2009), which has been
technically revised. It also incorporates the Technical Corrigendum ISO/IEC 19757-7:2009/Cor 1:2015.
The main changes compared to the previous edition are as follows:
— addition of validation of grapheme clusters such as 'n' followed by COMBINING GRAVE ACCENT
(U+0300) and a CJK unified ideograph followed by a variation selector.
— addition of the Unicode Ideographic Variation Database as a registry.
A list of all parts in the ISO/IEC 19757 series can be found on the ISO website.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO/IEC 2020 – All rights reserved
Introduction
ISO/IEC 19757 (all parts) defines a set of Document Schema Definition Languages (DSDL) that can
be used to specify one or more validation processes performed against Extensible Markup Language
(XML) documents. A number of validation technologies are standardized in DSDL to complement those
already available as standards or from industry.
The main objective of ISO/IEC 19757 (all parts) is to bring together different validation-related
technologies to form a single extensible framework that allows technologies to work in series or in
parallel to produce a single or a set of validation results. The extensibility of DSDL accommodates
validation technologies not yet designed or specified.
This document provides a language for describing character repertoires. Descriptions in this language
can be referenced from schemas. Furthermore, they can also be referenced from forms and stylesheets.
Descriptions of character repertoires doesn't need to be exact. Non-exact descriptions are made
possible by kernels and hulls, which provide the lower and upper limits, respectively.
The structure of this document is as follows. Clause 5 provides an informal overview of CREPDL.
Clause 6 specifies the syntax of CREPDL schemas. Clause 7 specifies the semantics of a correct CREPDL
schema; the semantics specify when a code point or code point sequence is in a character repertoire
described by a CREPDL schema. Clause 8 defines the behaviour of CREPDL processors. Finally, Annex A
describes differences of conformant CREPDL processors; Annex B provides examples of CREPDL
schemas.
Although the first edition was restricted to the validation of characters, this edition can also enable the
validation of grapheme clusters such as 'n' followed by COMBINING GRAVE ACCENT (U+0300) and a CJK
unified ideograph followed by a variation selector.
CREPDL schemas conformant to the first edition do not conform to this edition. In particular, this
edition changes the namespace name for CREPDL schemas.
© ISO/IEC 2020 – All rights reserved v
INTERNATIONAL STANDARD ISO/IEC 19757-7:2020(E)
Information technology — Document Schema Definition
Languages (DSDL) —
Part 7:
Character Repertoire Description Language (CREPDL)
1 Scope
This document specifies a Character Repertoire Description Language (CREPDL). A CREPDL schema
describes a character repertoire. A stream of UCS code points can be validated against a CREPDL schema.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements 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.
ISO/IEC 10646, Information technology — Universal Multiple-Octet Coded Character Set (UCS)
ISO/IEC 19757-2, Information technology — Document Schema Definition Language (DSDL) — Part 2:
Regular-grammar-based validation — RELAX NG
ISO/IEC 19757-4, Information technology — Document Schema Definition Languages (DSDL) — Part 4:
Namespace-based Validation Dispatching Language (NVDL)
W3C XML, Extensible Markup Language (XML) 1.0 (Fourth Edition), W3C Recommendation, 16 August
2006, available at http:// www .w3 .org/ TR/ 2006/ REC -xml -20060816
W3C XML-Names, Namespaces in XML (Second Edition), W3C Recommendation, 16 August 2006,
available at http:// www .w3 .org/ TR/ 2006/ REC -xml -names -20060816
IETF RFC 3987, Internationalized Resource Identifiers (IRIs), Internet Standards Track Specification,
January 2005, available at http:// www .ietf .org/ rfc/ rfc3987 .txt
Charsets I.A.N.A. IANA CHARACTER SETS, available at http:// www .iana .org/ assignments/ character -sets
Unicode, The Unicode Standard, The Unicode Consortium, available at http:// www .unicode .org/
CLDR, Unicode Common Locale Data Repository, The Unicode Consortium, available at http:// www
.unicode .org/ cldr/
UAX29, Unicode Standard Annex #29: Unicode Text Segmentation, The Unicode Consortium, available at
http:// unicode .org/ reports/ tr29/
UTS35, Unicode Technical Standard #35: Unicode Locale Data Markup Language (LDML), The Unicode
Consortium, available at https:// www .unicode .org/ reports/ tr35/
UTS37, Unicode Technical Standard #37: Unicode Ideographic Variation Database, The Unicode
Consortium, available at http:// www .unicode .org/ reports/ tr37/
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
© ISO/IEC 2020 – All rights
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