Why namespaces?

[Mark Birbeck]

James Tauber wrote:
> Mark Birbeck wrote:
> > Simon St.Laurent wrote:
> > > At 09:17 AM 9/1/99 +0800, James Tauber wrote:
> > > >"we would only need separate namespaces for each flavour of
> > > > XHTML if people are going to want to mix the three flavours
> > > > in the one document and distinguish the different usages
> > > > of the element/attributes names in the intersection."
> > >
> > > Simple, clean, cuts to the heart of the matter.
> >
> > 'fraid I don't agree. For the *legacy* HTML you may still need to
> > distinguish where it came from when it is being processed as XHTML.
> 
> But my point is that *namespaces* shouldn't be what you use 
> to make this
> distinction.

So, how else do you make the distinction? You can't use DTDs if the
XHTML is inside another doc - so what else?

> Namespaces (by my reading of the spec) are for distinguishing
> element/attribute vocabularies *within an instance*.

Not so. My server might receive this:

<com:delete>
    <u:user>
       <u:name>Mark</u:name>
    </u:user>
</com:delete>

and then five minutes later receive this:

<com:delete>
    <c:computer>
	    <c:name>laptop</c:name>
    </c:computer>
</com:delete>

By your reckoning the fact that the first document has 'com' and 'u'
distinct, and the second has 'com' and 'c' distinct is fine. But what if
the first delete instruction simply referred to removing the user
profile, and not the user? In other words, the two 'delete' nodes might
be in different namespaces and do different things, even though they are
not in the same document. My server would surely want to know which
namespace they occupied. Namespaces (by my reading of the spec) are for
distinguishing element/attribute vocabularies *within the whole world*.

Mark

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