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   Re: questions concerning RDF/DOM/XML Schema

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  • From: John Cowan <cowan@locke.ccil.org>
  • To: ***Marco Kleefman*** <mr_xyz@dds.nl>, XML Dev <xml-dev@ic.ac.uk>
  • Date: Thu, 20 May 1999 13:13:52 -0400

***Marco Kleefman*** wrote:

> Q1: Is statement1 [XML Schema] correct?

XML Schema is in its first public working draft, and no one can
say for sure how it will come out.  In particular, there may be
a separation between "lexical" and "syntactic" concerns which both
DTDs and the current version of XML Schemas intermingle.

> Q2: Does XML Schema has the possibility to describe the logical structure of
> a document?

Perhaps.  This question is very general.
> Q3: Is statement2 [DOM] correct?

> Q4: Is statement3 [RDF Schemas] correct?

RDF is a model of general metadata, not just structural metadata.
It can describe such non-structural questions as author, date of
creation, purpose, ... and can apply to non-XML-documents such as
photographs, printed books, records in conventional databases,
persons, houses, ....

> Q5: If XML Schema has the possibility to describe the logical structure of a
> document (see Q2), then what is the difference betweeen describing the
> logical structure in RDF-Schema or XML Schema?

RDF provides property-value pairs about arbitrary resources.  RDF
Schemas constrain which pairs can apply to which resources.
XML Schemas describe structural constraints on XML documents.
An XML schema might (if everything were done to that purpose)
be construed as a set of RDF statements.  An XML schema cannot
reasonably be an RDF schema: the universe of discourse is different.

> Q5: When you know everything about the physical structure of a document, you
> also know already a great deal about the logical structure of a document. Is
> this correct?

Maybe, maybe not.  All (valid) HTML documents share the same known DTD,
but may have no semantics in common whatever except a common
rendering model.  It was for this very purpose that XML was devised.
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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