RE: [xml-dev] Doctypes again (was Re: [xml-dev] Documents withindocuments)

[Robin Cover <robin@isogen.com>]

Re: "one of the weakest things about DTDs is that a
     document is considered valid if it meets the
     sender's criteria, whether or not it meets
     the recipient's"

Michael, is that a fair criticism of DTDs per se? 
At the formal level, a DTD provides a very weak basis
for a contract (whatever the type declaration) because
the semantics are opaque [1].  But a schema language
that's competent to express and validate semantics is
no better than a DTD if the two parties sharing the
conforming (instance) documents have not agreed on the
constraint "criteria" expressed in the schema.  It
seems that you're equivocating on the word "valid"
in this criticism of DTDs.

Or....?

Robin Cover

[1] "The SGML/XML Aversion to Semantics" at
http://xml.coverpages.org/sgmlEschewsSemantics.html

-----------------------------------------------------------------------

On Fri, 8 Feb 2002, Michael Kay wrote:

> > For me, the most compelling use for (the notion
> > of) document type is as a contract.  A document
> > type declaration asserts that a document's
> > syntax follows some set of rules to express the
> > document creator's intended semantics.
> 
> Yes. I've always thought one of the weakest things about DTDs is that a
> document is considered valid if it meets the sender's criteria, whether or
> not it meets the recipient's.
> 
> Michael Kay
> Software AG
> home: Michael.H.Kay@ntlworld.com
> work: Michael.Kay@softwareag.com
> 
> 
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