What are schemata

[Rick Jelliffe]

> From:  Tim Bray

> Hmm, this line of thought may be perpetuating what I see as one of
> the shortcomings of DTDs, namely that the DTD has to describe the
> whole document, i.e. a class of languages.  What about partial
> validation/constraints?  I think it's important that child-of-DTD
> support compond documents & partial validation.  So in the terms above,
> maybe these things define sets of elements and attributes, rather
> than whole documents. -Tim

I think Tim is making a very useful point here. I think provable
interconvertability with XML markup declarations is vital, but the future of
Web documents is going to include documents cut and pasted from multiple
fragments: not just fragment linking but physical editing too.

Some of these source fragments will have come from documents with XML markup
declarations, some with XSchema presumably, and some with none. So I think,
at least in the backs of our minds and preferably in the foreground, we
should enable such partially-declared documents with XSchema.

(This is actually not so contraversial: XML-data provides this, the HyTime
"Architectural Form" mechanism supports it, and WebSGML supports it to some
extent too. Elliot Kimber has posted in the past (words to the effect of)
that he thinks markup languages should move toward the view that markup
declarations in the prolog are really only the front part of an overlapping,
interlaced web of architectures (schemas). This is definitely the way the
XML on the Web is moving. HyTime already supports declarations using
different notations. )


Rick Jelliffe


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