RELAX NG

A Real-World Example: XHTML 2.0

Let’s leave our library for a while to look at XHTML. XHTML modularization breaks the monolithic XHTML 1.0 DTD into a set of independent modules described as in independent DTDs. Those modules can be combined to create as many flavors of XHTML as people may want. However, this has proven to be one of the most challenging exercises for schema languages. In their Working Drafts, the W3C HTML Working Group, the group in charge of XHTML, has published a set of RELAX NG schemas to describe XHTML 2.0. Its many interconnected modules illustrate the flexibility of RELAX NG to perform this type of exercises.

The solution chosen by XHTML 2.0 (see http://www.w3.org/TR/xhtml2/xhtml20_relax.html#a_xhtml20_relaxng for more detail) is to define each module in its own schema and then include all these modules in a top-level schema (called the RELAX NG XHTML 2.0 Driver). The driver schema looks like this:

 <?xml version="1.0" encoding="UTF-8"?> <grammar ns="http://www.w3.org/2002/06/xhtml2" xmlns="http://relaxng.org/ns/structure/1.0" xmlns:x="http://www.w3.org/1999/xhtml"> <x:h1>RELAX NG schema for XHTML 2.0</x:h1> <x:pre> Copyright &#xA9;2003 W3C&#xAE; (MIT, ERCIM, Keio), All Rights Reserved. Editor: Masayasu Ishikawa <[e-mail]> Revision: $Id: ch10.xml,v 1.7 2004/01/05 20:47:21 becki Exp $ Permission to use, copy, modify and distribute this RELAX NG schema for XHTML 2.0 and its accompanying documentation for any purpose and without fee is hereby granted in perpetuity, ...