James Clark has released a paper describing his perspective on the design of the RELAX NG XML schema language.

The paper represents Clark's personal perspective and is not an official work product of the RELAX NG technical committee at OASIS. Along with providing details about the reasoning behind the design of the language, it offers a sense of the possible merits or advantages of the language. The conclusion sums those up:

RELAX NG is designed to complement the XML 1.0 and XML Namespaces Recommendations. It is easy to learn and use, and has a level of complexity in the implementation and specification that is in the same ballpark as these Recommendations. It has a limited scope chosen on the basis of careful consideration of issues of modularity and layering. In particular, it restricts itself to dealing purely with syntax, and is thus, like XML itself, applicable to a wide range of application domains. It is a conservative, evolutionary refinement of well-proven ideas from SGML and XML DTDs. It is non-intrusive and aims to avoid unnecessarily constraining the freedom of schema authors to design their XML vocabularies as they see fit.