roddey at us.ibm.com
Fri Aug 7 20:12:40 BST 1998
>> Then the parser could see, even if a DTD came in from different sources via
>> different URIs, that in effect they were the exact same version and that
>> subsequent instances of the DTD could be just ignored and the current content
>Namespace names don't have to be dereferenceable:
>"http://www.ccil.org/~cowan/labor_yutz" is a perfectly good namespace name,
>even though there's nothing there (you'll get an error if you
>try to dereference it), because I assigned it and the namespace
>names beginning http://www.ccil.org/~cowan" belong to me.
Hmmm. Oh well, I guess the idea is still valid though in terms of DTDs and
Schemas in general. As they proliferate and go through versions, the ability to
assign some form of universal ID in such as way that applications can get that
information from the parser would be a very useful way of dealing with some of
the potential confusion that could arise. It would be pretty simple, avoid any
need for centralization, etc...
It would be particularly easy to apply it to Schemas and XML files, because it
would only require the agreeing on of a particular element type of attribute
type or extra blah="duh" statement in the <?xml ?> line perhaps. Since DTDs
don't have anything like that (do they?), I'm not sure how it would applied to
them, though they are the files that would best benefit from such a thing.
>In particular, there is no reason why the referent of the namespace
>name should be a DTD.
Ok, so I'm confused. Maybe its just a V vs. NV thing or something. If I define
a namespace, don't I also define a set of tags that are valid within that
namespace? I always assumed that the URL that the namespace mapped to would be
more than just a human readable unique identifier of some sort, and that it
would define the tags that legally belong to that namespace. I could see how
this would not be required for a NV scheme I guess, since it doesn't matter.
But for validation purposes, not being able to know that "Burping" was not a
valid tag within the "PoliteSociety" namespace seems like its missing out on
something important for many applications.
I can appreciate that just the partitioning of the global namespace has merit
in and of itself, but if you look at the use of namespaces in programming
languages (where I come from), its also important for them to have defined
content that can be validated against uses of them.
So am I missing something here? Do you mean its just not required, or that its
not been thought of at all?
IBM Center for Java Technology - Silicon Valley
roddey at us.ibm.com
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