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- From: David Megginson <email@example.com>
- To: Peter@ursus.demon.co.uk
- Date: Fri, 11 Apr 1997 09:10:51 -0400
Peter Murray-Rust writes:
> What follows is the meta-DTD, right? And the system knows it's
> a meta-DTD because of the inclusion of one or more <?ArcBase PIs?
No, it's a derived DTD (actually, a DTD for a document that implements
a derived architecture). A meta-DTD will not usually have an
<?ArcBase ..?> PI, unless it is mapped to yet another meta-DTD.
If you write a DTD, and include
in that DTD, you are suggesting that your DTD uses HTML as a base
architecture. The HTML DTD is the meta-DTD, and it is not modified in
> What this is doing is mapping elements in different DTDs to the
> same element in your meta-DTD. This implies that they are synonyms
> in some way. Does it assume that they have the same content model,
> attributes and that the elements in the content model have
> (recursively) been mapped onto the DTD. Or are you essentially
> aliasing SYM in HTML to SYMBOL and SYMBOL in MATH to SYMBOL but
> having to provide different content models and processing for each?
No, it's the other way around -- the DTD for the derived architecture
maps some of its elements to those in one or more meta-DTDs (though
you don't have to do the mapping in the DTD itself). If you're
creating document type X, and you're including architectures from
CALS, HTML, and TEI-L, then you put the mappings in the X DTD.
They don't have to have exactly the same content models -- the content
model in the derived DTD can be more restrictive (but not less).
> This means your DTD is a superset of the other DTDs and your own elements?
Not exactly -- it means that there is an intersection between the
semantics of your DTD and the semantics of each of the meta-DTD. Your
DTD may have element types that are not in the meta-DTD, and the
meta-DTD may have element types that are not in your DTD.
> I think I start to understand. By 'structure' you mean the tree structure
> of each DTD? In which case AFs are a way of providing multiple views of the
> same document?
I don't follow.
All the best,
David Megginson firstname.lastname@example.org
Microstar Software Ltd. email@example.com
University of Ottawa firstname.lastname@example.org
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