xml-dev - Re: Question on ANY (its use in RDF)

[Dan Brickley <Daniel.Brickley@bristol.ac.uk>]

On Mon, 25 Jan 1999, Chris Maden wrote:

> [Marcus Carr]
> > Roger L. Costello wrote:
> > > I have a question about the ANY type.  It is my understanding that
> > > an element defined to be of type ANY can contain any element that
> > > is defined *within* the DTD (i.e., it cannot use elements that are
> > > not defined in the DTD).  Correct?
> 
> Correct.
> 
> > My advice to anyone is never accept a DTD that uses ANY. The only
> > legimate use I have ever seen for it is in an interim DTD during
> > data conversion. It's a sloppy use of a sloppy mechanism - for
> > example, would you really want to support an infinite number of
> > nested rdf:Description elements? There is no preventing this - even
> > the DOCTYPE element can be nested within itself.
> 
> However, remember that a document type is composed of its formal
> specification *and* its prose specification.  Moreover, RDF is
> explicitly intended for use with namespaces.  The RDF DTD expresses
> constraints among RDF elements; using ANY in the content model of its
> root was a good idea, just like HyTime uses ANY for most of its
> content models.  Though I don't think the spec explicitly says so, RDF
> is more akin to an architecture than to a document type, but without
> the ability to rename element types.

This is probably true, but there is no 'RDF DTD' as such. The rdf.dtd
thing is I believe something experimental found on IBM's Alphaworks site
and not from the RDF Model and Syntax spec.

Dan



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