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- From: costello@mail11.mitre.org (Roger L. Costello)
- To: xml-dev@ic.ac.uk (XML Developers' List)
- Date: Fri, 15 Jan 99 13:24:21 -0500
I have been closely monitoring (with great interest!) all the discussion
arising from my question on what is a namespace. It seems that people have
differing ideas on what it is. I would like to try to summarize the points
of view, and add my own two cents.
(1) A namespace is just a URI. It references some domain. It is simply
there to tell an application/processor what domain the associated XML
elements hail from.
(2) A namespace is a URI to a DTD. It references a domain and also a DTD
within the domain. In addition to telling an application/parser what
domain the associated XML elements hail from, with this namespace
declaration a validating parser could validate that portion of your XML
document against the DTD at that URI.
So, with point-of-view (2) this is a valid namespace declaration:
<BookCatalogue xmlns="file://localhost/BookCatalogue.dtd">
and this is not a valid namespace declaration:
<BookCatalogue xmlns="file://localhost/">
because there is no referenced DTD at that domain.
Is this a fair assessment of the points of view?
My two cents:
What is the purpose of namespaces? It is my understanding that the purpose
of namespaces is twofold:
(a) Disambiguation. e.g., if BookCatalogue is defined in another
DTD that you are using then namespaces allow you to distinguish
BookCatalogue in DTD A from Bookcatalogue in DTD B
(b) Reuse/validation. e.g., if you declare that BookCatalogue
comes from a DTD in some domain then conceivably a parser
could validate that portion of the XML document.
Who's right? What is "truth"? /Roger
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