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Re: Namespaces, schemas, Simon's filters.
- From: Richard Tobin <email@example.com>
- To: firstname.lastname@example.org
- Date: Thu, 23 Aug 2001 22:30:45 +0100 (BST)
>Actually, while I've argued as to why making local elements unqualified is a
>good thing from the point of view of what local elements are, no one has
>given a similar argument for why local elements should be qualified. The
>arguments in favor of qualifying them have been simply "I don't like
>unqualified elements because I can't use the namespace to uniquely identify
>the element" - when namespaces fail to uniquely identify different local
A fair question. To elaborate it a bit, the argument is that if you
need the containing-element context to identify the element, then it
makes no difference whether it's qualified or not because you can only
interpret it in that context.
Two reasons spring to mind:
- Even if it doesn't tell you exactly what it means, it still tells
you where to go to find the answer. It's immediately clear that
it's *one* of the the foo elements from the xyzzy namespace.
- Often (take that with a pinch of salt: like most people, I've only
written a few schemas) all the foo elements in the xyzzy namespace
*mean* the same thing. It's just that some of them are restricted
in different ways because of the context. For example, in my
serialization of the XML infoset, the <children> child of the
<documentTypeDeclaration> element and the <children> child of
the <element> element are both in some sense the same thing, but
the allowed content is different and by using local elements
I can give them different content models and get better validation.
After all, if they weren't in some way the same I wouldn't have given
them the same name.