DTD vs Schema

John Cowan cowan at locke.ccil.org
Thu Sep 10 19:10:58 BST 1998

David Megginson scripsit:

> I still haven't had time to give XSchema a proper going-over, but from
> what I've seen, XSchema and DCD are not competing for the same
> territory:
> - XSchema defines an instance-based representation of DTDs
> - DCD defines an alternative to DTDs

Just the opposite: it is a stated requirement of DCD that it represent
everything a DTD can, whereas XSchema long ago abandoned that
requirement.  In particular, XSchema does not handle entities (someday,
information about unparsed entities may be added).

DCD instances are by intention RDF metadata, though the current version
has both intentional and unintentional deviations from the current
RDF Model & Syntax draft.  DCD also has a concept of "datatypes"
that identify the internal (non-XML) syntax of #PCDATA.

XSchema has an emphasis on reusability, although the actual mechanism
of reuse hasn't been designed, pending the next XLink draft.

Personally, I would like to see a convergence between the two, as
I think they *are* competing for the same territory.  The DCD concept
of RDF-compliance is IMHO the Right Thing, whereas XSchema has a bit
better thought out view of what to include.

John Cowan	http://www.ccil.org/~cowan		cowan at 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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