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I use RELAX NG for my purposes. You can get details about RELAX NG from
http://www.relaxng.org
The following are purely my opinions, and the information I have gathered.
RELAX NG is understandable and this is what academics use. RELAX NG is
accepted in Japan as the standard, it is taught in schools in Japan,
including the framework of regular tree grammars.
The framework of regular tree grammars has found acceptance in several
universities in US, which include University of Washington, Seattle,
University of California, San Diego, University of California, Los
Angeles, and University of Pennsylvania. These are the universities where
I know there is work going on using regular tree grammars.
These places have also found W3C XML Schema to be complicated and not that
worthwhile. Further more, the processing of W3C's XQuery is based on
regular tree grammars, though the initial typing might look as if it
conforms to W3C XML Schema.
Furthermore, there is some research at UCLA which argues that RELAX NG is
better than W3C XML Schema for database modeling - the only thing that W3C
XML Schema tried to solve, neglecting text modeling. Text modeling people
use DTDs as they do not need data types to this date.
It just so happens that RELAX NG came after W3C XML Schema, from the
terrible discontent with W3C XML Schema. It is a very good schema
language, and the design of the language is so very carefully thought of.
The design principle can be summarized as -- collect requirements, then
think really well about how to support them, and come up with
mathematically elegant solutions which will support all the requirements.
Who is pushing W3C XML Schema -- it seems like Oracle is one of the
biggest pushers of this technology, the reason they say is they already
have committed several dollars to W3C XML Schema. Even though they
understand that RELAX NG is better than W3C XML Schema, they are finding
it difficult to switch.
I do not think such above restrictions as what Oracle faces applies to
academic research. Furthermore, all we will say is industries should
slowly start supporting RELAX NG also. I am sure there will be a migration
at some point of time, question is when..
The above is as unbiased an analysis as possible of the current state of
affairs. I will say RELAX NG is a beautiful language -- simple, elegant,
easy to use, and applies to several application scenarios several people
have come across.
<warning>speaking for himself only</warning>
cheers and regards - murali.
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