[January 19, 1999] A submission to the W3C on January 5, 1999 has been published as a NOTE, "Document Definition Markup Language (DDML) Specification, Version 1.0." References: NOTE-ddml-19990119, W3C Note, 19-Jan-1999. The editors are: Ronald Bourret (Darmstadt University of Technology), John Cowan, Ingo Macherius (GMD), and Simon St. Laurent. The editors suggest that the specification serve as input for the W3C XML-Schema-WG.
Document abstract: "This document proposes Document Definition Markup Language (DDML), a schema language for XML documents. DDML encodes the logical (as opposed to physical) content of DTDs in an XML document. This allows schema information to be explored and used with widely available XML tools. DDML is deliberately simple, providing an initial base for implementations. While introducing as few complicating factors as possible, DDML has been designed with future extensions, such as data typing and schema reuse, in mind."
DDML was formerly known as XSchema, and represents a cooperative effort of members of the XML-Dev mailing list. For a list of differences between DDML and XSchema, see Appendix B, "Differences between DDML and XSchema". Historical information regarding the development of DDML is available at http://purl.oclc.org/NET/ddml. Inquiries from the public or press about this submission should be directed to Ronald Bourret (technical) or Klaus Birkenbihl (legal).
See also the Submission Request and the W3C Staff Comment. In the comment, Dan Connolly writes: [The submission represents] "a rather straightforward adaptation of XML DTD functionality into XML element and attribute syntax. Translation from DDML to XML DTD syntax is an explicit design goal, and translation in the other direction is discussed. An interesting aspect of the proposal is that translation is not 100% lossless in either direction (for example, comments, processing instructions, and parameter entities do not translate without some loss). The practical trade-offs in this area lead to interesting design choices."
"Document Definition Markup Language (DDML) Specification, Version 1.0." NOTE-ddml-19990119. 19-Jan-1999. [local archive copy]
XSchema - DDML predecessor
Other XML schema design:
- W3C XML Schema Working Group - Co-chaired by Dave Hollander of Hewlett-Packard and C. M. Sperberg-McQueen of the University of Illinois at Chicago.
- DCD - Document Content Description for XML
- SOX - Schema for Object-oriented XML