xml-dev - Re: Common XML (was Re: Document Feature Requirements)

[David Megginson <david@megginson.com>]

Sean McGrath <sean@digitome.com> writes:

> [David Megginson]

> >You might be a little overly optimistic in assuming that any markup
> >has good survival characteristics in the general case -- it's the
> >model that matters, not the markup.
> 
> I have read the above 5 times now and I'm afraid it has gone
> over my head. Can you explain what you mean by this?

XML is an interchange format -- that means that it's used to exchange
information that follows some other model.  When the XML passes
through a non-XML system and comes back out as XML on the other end,
only those things that are represented in the model are likely to come 
out again.

This is not so noticable with documents (I know that a lot of people
hate the document/data distinction, but live with guys), because a lot
of them follow a model (as expressed in the Infoset and implemented in
DOM, XPath, etc.) that is very close to the XML representation itself;
this is *very* noticable with data, which tends to pass through
application-specific RDF tuples, Perl objects, SQL tables, C
structures, etc., and come out on the other end completely changed,
especially if there is more than one possible XML representation for
the same logical information.


All the best,


David

-- 
David Megginson                 david@megginson.com
           http://www.megginson.com/

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