Those who've been knocking around the XML or Web development communities for any length of time have come across the work of James Clark, if not evidence of the man himself. His is a pretty fascinating story, which you can read more about on his bio page.
For the purposes of our discussion, let's just say he's been around the SGML and XML communities since the early 90s and has contributed a substantial and extremely useful body of work. His highlight reel includes an open source SGML parser he wrote in C, acting as technical lead during the development of the XML 1.0 Recommendations, enhancing SGML to make XML a formal subset of SGML, development of expat, "the world's fastest XML parser," co-authoring the XSL submission, editing the XSLT and XPath Recommendations, and last and most relevant, developing TREX, a schema language for XML that pre-dated (and many believe outclasses) XML Schema.
In fact, TREX plus another alternate XML schema language named RELAX, gave rise to RELAX NG (where NG stands for Next Generation), which is an OASIS development project and is now also enshrined as ISO/IEC standard 19757-2. This probably explains why most of Clark's recent work centers around RELAX NG and includes an open source validator for that markup language (Jing), a tool for converting XML DTDs into RELAX NG (DTDinst), a Java program that translates RELAX NG schemas into other formats (Trang) and a new
To continue reading for free, register below or login
To read more you must become a member of SearchSOA.com
XML mode for GNU Emacs that performs incremental XML parsing and does RELAX NG validation.
Why bother with RELAX NG when there's XML Schema, a W3C recommendation also available? Three short answers explain why this markup language is worth digging into:
All of this goes to explain why RELAX NG is so widely used and why it still enjoys a reputation as an attractive, if not compelling, alternative to XML Schema to this very day. ISO Standard status doesn't hurt much, either, especially in Europe where this kind of official seal of approval often means more than it does in the states.
You can dig deeply into RELAX NG, through many avenues (including the aforementioned bio page for Clark himself), but the following sites offer outstanding entry points:
Those who need to build schemas for XML documents or document collections and who've been frustrated by XML Schema may find RELAX NG preferable. Check it out, and you may come to share this viewpoint.
About the author
Ed Tittel is a full-time writer and trainer whose interests include XML and development topics, along with IT Certification and information security topics. Among his many XML projects is the 2002 Sybex book XML Schemas, which he co-authored with Chelsea Valentine and Lucinda Dykes (ISBN: 0792140459). E-mail Ed at etittel@techtarget.com with comments, questions or suggested topics or tools for review.
