DTD, XML schema, RDF,RELAX which one

[cutlass <cutlass at secure0 dot com>]

been lurking for awhile on this list, thx in advance
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i have a repository of objects defined with xml, with which i need to 
have a:
- basic common definition with a wide variety of binary objects ( read 
pictures, html, text, etc )
- method of inheritance of attributes and methods ( read classes and 
instances)
- remote and local transformation of xml through XSL ( read SOAP/XML-RPC )

i have done this successfully ; i stuck with DTD as  my base schema and 
validating method

vague definition of problem, yes, but the question i have is multiple 
choice ( or not ), with respect to schema definition:

- should i stick with DTD, due to innate fear the below technologies 
won't stick ( and parsers aren't supported )
- go the whole hog with RDF, and gain the benefits of their lovely 
inheritance structure
- XML schema
- figure out how Schematron and RELAX fit in the picture

i have posted here, as i choose XSL in january as the key technology 
that the repository interacts with; and i am extremely happy that XSL 
'sticked'. i have also found that when looking through everything with 
XSL specs on; it affects architecture decisions ( read interfacing with 
xml databases, etc ).

there are some conflicting issues , think inheritance: one can inherit a 
document via
- xsl:import or xsl:include
- document()
- or through schema definition

these all have impact on which technology i choose with respect to using 
XSL. At the moment DTD are becoming cumbersome and manipulating them are 
creating side effects due to non-native xml format. IN addition, i can 
see a time where severe limitations will occur due to delaying my choice.

a simplified version of question;

" Which schema and validation technology is going to be the best choice 
when using XSL in the short, medium and long term future "

regards, jim fuller


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