XSchema: multiple proposals

John Cowan cowan at locke.ccil.org
Wed Jun 3 20:32:34 BST 1998

Toby Speight wrote:

> Hmm.  I see your point.  I think what I dislked about Ron's proposal
> is the unconstrained #PCDATA here:
> Ron> <!ELEMENT NotationValue (#PCDATA)>
> Ron> <!ELEMENT EnumerationValue (#PCDATA)>
> I think that the list-of-elements structure can be retained, but with
> tighter constraints by writing
> > <!ELEMENT NotationValue EMPTY>
> > <!ATTLIST NotationValue Value NMTOKEN #REQUIRED>
> > <!ELEMENT EnumerationValue EMPTY>
> > <!ATTLIST EnumerationValue Value NMTOKEN #REQUIRED>

That's what my draft does wrt enumerations.  I have more problems
with notations, because it doesn't make sense to me to have to
redeclare every notation name with every notation attribute,
since any notation attribute can refer to any notation name.
Thus I treat notation attributes like other attributes with
predefined types.
> John> Now that is an excellent idea!  However, it would be necessary
> John> to permit arbitrary XML markup within the doco, so a content
> John> model of ANY is probably the right thing here.
> I'd like to agree at least some conventions here, but I think we
> should defer the details until later.  For the moment, I think we
> should concentrate on *where* we can put documentation.

Agreed.  I'll think about it.
> With IDREF, we could keep the documentation separated from the schema, but
> I'm a follower of the theory which says that the closer the documentation
> is to the code, the more likely they are to correspond.

I think that's best also.
> I don't think this is really workable.  We don't have SUBDOC in XML,
> nor do we have anywhere in the XSchema DTD that we can insert another
> tree rooted at XSchema.

For me it would be easy to add DOCTYPE (my root type) as another
top-level type co-ordinate with ELEMENT, ENTITY, and NOTATION.

> Even if the mechanics can be made to work,
> I'm concerned about ID clashes.  Can namespaces help prevent this?

Yes, particularly if there were some way to say "Colon-free names
brought in from this schema have an implicit 'ns' of xxxxx".

> I'm not convinced about wanting only to link-in whole XSchemas, either:
> it seems to me that lots of people would want P[aragraph] (and its
> children) from HTML, for instance.

I'll consider that.  But linking in HTML4.0:P brings in a lot of
baggage, specifically its content model, which includes virtually every
other HTML body tag.  I suspect that DTDs (and, a fortiori, XSchemas)
tend to be far more closely interwoven than people really suspect.

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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