From: Lachlan Hunt <lhunt07@postoffice.csu.edu.au>
>
> AaronEldreth@cs.com wrote:
>
> > The DTD would simply tell the browser how to interpret the If...then, 
> > else, case and other handlers. XML or at least XHTML would be 
> > stretched from a SGML based language, to a universal programming 
> > language capable of doing anything.
>
>   XHTML is not and should not be a programming language.  XHTML is 
> called "Extensible HyperText Markup Language", NOT "Extensible HyperText 
> Multipurpose Language", and, therefore, it is designed for marking up 
> structure in documents only, and that's how it should stay.  Scripting 
> XML documents is the domain of the Document Object Model [DOM] and the 
> scripting language standards, like ECMAScript [ECMA-262].
>
> [DOM] http://www.w3.org/DOM/ 
> [ECMA-262] 
> http://www.ecma-international.org/publications/standards/Ecma-262.htm 

While it would  be possible to write an SGML DTD that would check
for the validity of some ECMAScript, in either a separate file or
as part of an (X)HTML file, I'd have to question its utility.  At best
it would have the ability to check that it's syntactically valid,
and that is but a small part of what I would want from anything that
verified a script file.  Besides, using a DTD for that purpose is
 akin to using a piledriver to crack nuts. It could do it,
but it probably isn't worth the effort it would take to ensure you
get shelled nuts and not nut butter.

 (Given the subset of SGML that XML is, I don't think it's possible
 to generate an XML DTD that would check for the syntactic
validity of ECMAScript , but I may be wrong.)