A New Hope (was Re: Storing Lots of Fiddly Bits (was Re: What is XML for?))

Rick Jelliffe ricko at allette.com.au
Fri Feb 5 16:02:28 GMT 1999

 From: spreitze at parc.xerox.com <spreitze at parc.xerox.com>

>Right!  I think a significant part of the problem here is that people
are realizing that XML's data model is not as expressive as they'd like.
For example, XML's entity structure looks like a semi-labelled graph
(vertices are labelled (with entity tags) but edges are not labelled),
whereas many other data models (e.g., RDF) let you label both the edges
and the vertices.

HyTime lets you label edges too: anyone can use that (to those people
who whinge "but it is too hard" I say "CORBA CORBA CORBA": some things
are big and difficult, it doesn't mean they are therefore bad). The
question is, should such labelling be part of the language at the
lexical level (which XML deals with) or a further layer. It is the old
tradeoff that a general purpose system will (probably) be worse at any
specific task than a specific system.

> It seems to me that one plausible way out of this conundrum is for the
XML Schema WG to recognize (1) the need for schemas to be written in
terms of more expressive data modelling systems, (2) the need to support
a variety of encodings of those data models into XML, and (3) the need
for a schema to describe a particular encoding (the one desired for the
schema at hand) of the schema's data model into XML.

Sounds good. But Mike's comments do betray a wish that XML operated on
some other level than the strictly lexical: but it doesn't, except by


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