namespaces discussion

[Richard L. Goerwitz III]

> Say my book DTD has:
> 
> <!ELEMENT div (%base.div.content;|%extended.div.content;)>
> ... 
> <!ENTITY % mathml.dtd SYSTEM "mathml.dtd">
> <!ENTITY % pgml.dtd SYSTEM "pgml.dtd">
> %mathml.dtd
> %pgml.dtd
> 
> <!ENTITY % extended.div.content "math|pgml">
>
> And bingo!, I can use MathML and PGML in my Book.

For XML, of course, you need to add semicolons to the parameter
entity references, and make sure that this is all in the external
DTD subset (because of the PEs being used in an ELEMENT decl).
You then also have to put your % extended.div.content decl before
the ELEMENT div decl.

But assuming all this was done, you'd still have to have full
control over the mathml and pgml DTDs, to make sure they didn't
define any of the same elements as each other - or your Book
DTD.

It's all one namespace, and XML doesn't allow element redefini-
tion.


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