Namespace questions

Chris Maden crism at
Thu Jul 2 17:14:24 BST 1998

[Ron Bourret]
> 1) Can I have multiple prefixes in the same file that point to the
> same namespace?  The namespace spec doesn't appear to prohibit this.

I believe so, but the ramifications of this aren't clear.  I don't
want to touch this question, really.

> 2) How do namespaces and XLinks work together?  For example, suppose
> I link to the <Foo> element in another file.
> a) If the <Foo> element is prefixed (that is, it is really
> <Bar:Foo>) does my pointer need to know this?

Yes.  Your pointer points to something in a document *instance*, not
to a class; so whether it's <Bar:Foo> or <FooBar> or <_>, you just use
the GI as given in that document instance.

> b) When I get the <Foo> element back as a result of resolving the
> link, do I get <Foo> or <Bar:Foo>?  And if I get <Bar:Foo>, do I
> also get a namespace PI telling me about the Bar prefix?

Possibly the hardest thing about XLink is that it *doesn't return
anything*; you *don't get anything back*.  The pointer points; it
doesn't fetch.  When you point to <Bar:Foo>, what you have is a
pointer to <Bar:Foo>.  That's it.  Now, if you're writing a program
based on top of a parser and an XLink processor, you should probably
be able to ask the parser for some information about the thing that
the pointer is pointing to, such as its namespace.  But that's
something *on top of* XLink, not part of it.

<!ENTITY crism PUBLIC "-//O'Reilly//NONSGML Christopher R. Maden//EN"
"<URL> <TEL>+1.617.499.7487
<USMAIL>90 Sherman Street, Cambridge, MA 02140 USA" NDATA SGML.Geek>

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