ISO IEC 19757-7-2020 PDF

Full title and description

Information technology — Document Schema Definition Languages (DSDL) — Part 7: Character Repertoire Description Language (CREPDL). This international standard specifies CREPDL, a language for describing character repertoires so that a stream of UCS (Universal Character Set) code points can be validated against a CREPDL schema.

Abstract

ISO/IEC 19757-7:2020 defines the Character Repertoire Description Language (CREPDL). CREPDL schemas describe character repertoires (including kernels and hulls where applicable) and provide rules and semantics for determining whether individual UCS code points belong to a described repertoire; the standard also specifies processor behaviour and gives examples.

General information

• Status: Published / confirmed international standard.
• Publication date: August 2020 (publication implemented 2020-08-05).
• Publisher: ISO/IEC (ISO/IEC JTC 1/SC 34 responsible committee).
• ICS / categories: 35.240.30 (IT applications in information, documentation and publishing).
• Edition / version: Edition 2 (2020).
• Number of pages: 15 pages (PDF publication).

Scope

This part of ISO/IEC 19757 specifies a language (CREPDL) for formally describing character repertoires that can be used when validating text and XML-related data. A CREPDL schema expresses which UCS code points belong to a repertoire; processors implementing the standard evaluate streams of UCS code points against such schemas. The document includes syntax and semantic rules, treatment of repertoire kernels and hulls, processor requirements and illustrative examples.

Key topics and requirements

• Definition of CREPDL syntax and schema structure for describing character repertoires.
• Formal semantics that determine whether a UCS code point is in a described repertoire (including kernels and hulls concepts).
• Rules for validating a stream of UCS code points against a CREPDL schema.
• Specification of CREPDL processor behaviour and conformance differences.
• Normative references and interoperability context (e.g., relation to ISO/IEC 10646, XML-related DSDL parts such as RELAX NG, and relevant IETF/Unicode references).

Typical use and users

CREPDL is used by standards authors, XML and text-processing tool implementers, validation-tool developers, archivists and publishers who need formal character-repertoire specifications, and organizations defining restricted or application-specific character sets (e.g., for identifiers, controlled vocabularies, legacy-data validation, or language-support profiles). It is particularly relevant where precise, machine-checkable descriptions of allowed characters are required.

Related standards

ISO/IEC 19757 (DSDL) family (other parts such as Part 2 — RELAX NG), ISO/IEC 10646 (UCS / Universal Character Set), Unicode Standard references and relevant IETF specifications (for example, RFC 3987 for IRIs) are related and commonly referenced alongside CREPDL. Previous edition ISO/IEC 19757-7:2009 was withdrawn and superseded by the 2020 edition.

Keywords

CREPDL, character repertoire, UCS, Universal Character Set, DSDL, validation, character set description, XML validation, ISO/IEC 19757, RELAX NG, ISO/IEC 10646.

FAQ

Q: What is this standard?

A: ISO/IEC 19757-7:2020 is the DSDL Part 7 standard that defines CREPDL — a formal language for describing character repertoires so that streams of UCS code points can be validated against those descriptions.

Q: What does it cover?

A: It covers CREPDL schema syntax and semantics, concepts such as kernels and hulls of repertoires, rules for validating UCS streams, processor behaviour and examples to illustrate usage.

Q: Who typically uses it?

A: Implementers of validation tools and XML processors, standards and specification authors, software developers dealing with character set restrictions, archivists and publishers requiring precise character-repertoire control.

Q: Is it current or superseded?

A: The 2009 edition was withdrawn; the current edition is ISO/IEC 19757-7:2020 (Edition 2, published August 2020). The publication was reviewed and confirmed as current in ISO system review (confirmed in the review cycle).

Q: Is it part of a series?

A: Yes — it is Part 7 of ISO/IEC 19757 (Document Schema Definition Languages, DSDL). Other parts of the series (for example Part 2 — RELAX NG) address different validation languages and tools used in the XML ecosystem.

Q: What are the key keywords?

A: CREPDL, character repertoire, UCS, DSDL, validation, ISO/IEC 19757, character set description.