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   Re: words (RE: extensibility in XSchema?)

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  • From: John Cowan <cowan@locke.ccil.org>
  • To: XML Dev <xml-dev@ic.ac.uk>
  • Date: Mon, 22 Jun 1998 17:11:51 -0400

Peter Murray-Rust wrote:

> Now compare MIME:
>         If I get sent a file of type image/gif I can:
>         - determine that 'image/gif' is a MIME type
>         - see if it is in the central IETF registry. If so I can read the formal
> definition, etc.
>         - *and most important for me* I can associate the MIME type with a program
> through the mailcap file, *even if the MIME type is not registered*.
> This is all I am asking for, but there seems to be no way to do a similar
> thing for an XML element or attribute.

The trouble, IMHO, is not so much that an "elemcap" file couldn't
be created; it's what to put in it.  MIME types describe fairly
large objects with little structure, except for the multipart/*
types, and their structure is just a list of objects with
MIME types, so simple recursion does it all.  When you've got
down to the non-multipart level, you can reasonably run a program
on each resulting MIME object.

In XML documents, though, you can't reasonably run a program on
each element, unless the programs are very lightweight.  That
seems to me to be what DS+L (I can't remember the number of S's)
is all about: associate a Scheme program with every element
according to a hierarchical rule, and then run that program
to interpret the element.

Unfortunately, people seem to have fallen into the "report-generator"
syndrome: the desire to do everything that's possible in a programming
language, using something that's simpler than a (Turing-complete)
programming language.  Hard to do.

John Cowan	http://www.ccil.org/~cowan		cowan@ccil.org
	You tollerday donsk?  N.  You tolkatiff scowegian?  Nn.
	You spigotty anglease?  Nnn.  You phonio saxo?  Nnnn.
		Clear all so!  'Tis a Jute.... (Finnegans Wake 16.5)

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