Another look at namespaces

Fri Sep 17 15:20:34 BST 1999

-----Original Message-----
From: Tim Bray <tbray at textuality.com>
To: XML-DEV <xml-dev at ic.ac.uk>
Date: Thursday, September 16, 1999 12:46 PM
Subject: RE: Another look at namespaces

>At 08:30 AM 9/16/99 -0700, Andrew Layman wrote:
>>With all due respect to Simon St. Laurent, I believe that Tim Berners-Lee
>>was correctly precise when he wrote "the document corresponding to the
>>namespace URI becomes
>>the place where the namespace-author can put *definitive*
>>information about the intent of the namespace."
>
>I and many others disagree, for reasons best expressed in Jon Bosak's
>summary of the issues.  Among other things, I don't believe that most
>interesting namespaces *have* definitive information, but have semantics
>that are communicated via some messy combination of schemas, stylesheets,
>prose documentation, and running code.

We either have a different use of words or a very serious
problem.  Whereas with natural langauge, meanings change and
grow and everyone has slightly different associations with a word,
in computer languages we need to build on top of XML we need
to have the ability to define meaning precicely in terms of
other existing languages.

If you believe that "HTML 4.0" specification  - and a schema for XHTML -
can decied that <p> cannot occur in <head> then do you not grant
th ewriters of the spec the right to make that definitiove assertion (in
prose
or schema) whatever code someone may or may not write to produce or
parse <p> inside <head>

>>While there are many processes that can be applied to a document, and
>>correspondingly many specifications of those processes, there can be, for
a
>>given term in a namespace, at most one correct *definition*.
>
>I disagree, I think this is a strong and surprising claim, and I would
>like to see some real-world supporting evidence.

We are designing this, not investigating it as a natural phenomenon.

This is my understanding of the history of for example RDF and namespaces.
The RDF M&S working group decided it needed a way
for system designers to define new vacabularies for new data models.
They realized that while using XML was something they had been asked to do,
they would need a way of creating new modules of meaning.
The XML working group then explainted that they were producing that
functionality in XML, and so (as with atomic data types) the RDF
group decided to simply hang of teh XML namespace functionality.

This implies taht the meaning of an RDF property (conveyed by an XML
element)
is defined by the namepsace it is in.   My assumption - in which I don't
think I was alone - was that this meaning could be (either of course
programmed strighht into a specific application) or information about it
could be put into the schema.   The RDF spec, indeed, defines the
relationship between the name and an element of the schema (one
of the bits which needs to be tracked byeween xml and rdf schemas)

I had assumed that the xml schema work would allow definitive information
about content models to be put into the xml schema.

My understanding was also that because one document can contain
information form more than one language, that one schema document,
optionally available at the namespace URI, would contain both
xml-schema language and rdf-schema language.

This is IMHO a very nice arrangement in fact.

Perhaps perception of it is clouded bythe fact that XML 1.0 doesn't mention
namespaces at all, and XML NS does not mention schemas at all.
In other words, the specs -- having to only refer backwards in time --
have not been good at pointing to how the future architecure will fit
together.

Tim BL
in no official capacity.

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