RELAX NG now a full ISO International Standard
12:00, 15 Dec 2003 UTC | Michael Smith

James Clark has announced that the RELAX NG schema language was published by the ISO as an International Standard on December 1st.

He writes:

I have just been informed that RELAX NG was published by ISO as an International Standard on 1st December 2003. The full title is:

ISO/IEC 19757-2:2003
Information technology -- Document Schema Definition Language (DSDL) --
Part 2: Regular-grammar-based validation -- RELAX NG

Its ISO Catalogue entry is:

In a follow-up message, he indicates that the RELAX NG compact syntax is also slated to become an official part of the standard, as a new normative Annex.


RELAX NG was developed under the guidance of Clark and MURATA Makoto (creator of the original RELAX schema language) and the members of the RELAX NG technical committee at OASIS. Work on making it an ISO standard was subsequently taken on by the Document Description and Processing Languages subcommittee of the ISO/IEC Joint Technical Committee 1 (ISO/IEC JTC 1/SC 34), as part of a larger project, the Document Schema Definition Language (DSDL), which has as its objective to:

create a framework within which multiple validation tasks of different types can be applied to an XML document in order to achieve more complete validation results than just the application of a single technology

Some of the features for which RELAX NG is noted include:

  • simplicity and ease of learning and implementation
  • makes no changes to the information set of an XML document
  • treats XML attributes and elements uniformly as much as possible
  • has unrestricted support for mixed content and unordered content
  • is datatype-neutral and so can partner with a separate datatyping language (such as W3C XML schema datatypes)

Clark has described the language in general as a "conservative, evolutionary refinement of well-proven ideas from SGML and XML DTDs".

RELAX NG is supported by a large number of tools, including tools for converting RELAX NG schemas to and from DTDs and W3C XML Schemas, and an innovative XML editing mode for GNU Emacs that does incremental parsing and validation of document instances. It has also become widely used by groups developing other standards, including some W3C working groups.

To paraphrase another user, an appropriate slogan for RELAX NG might be:

Make your life easier: Use RELAX NG

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