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Re: TB16 Re: Comments on arch doc draft

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Wed, 03 Jul 2002 20:28:42 +0300
To: ext Paul Prescod <paul@prescod.net>, WWW TAG <www-tag@w3.org>
Message-ID: <B9490EFA.17D19%patrick.stickler@nokia.com>

On 2002-07-03 19:06, "ext Paul Prescod" <paul@prescod.net> wrote:

> Patrick Stickler wrote:
>> 
>> ...
>> 
>> Using an http: URL to denote a rock in my back yard or the concept of
>> 'spicy' does not make either of those things web-accessible or
>> the latter concrete.
>> 
>> And if those URLs really *do* denote those non-web-accessible things,
>> then putting anything else at that URL which would be accessible
>> is a bug.
> 
> Nobody is talking about "putting something else at that URL." Rather
> they are talking about making it such that doing a GET on the rock's URI
> returns a *representation of the rock*. The thing at the URL is still
> the rock. But rocks can't move over the Internet so the GET fetches the
> next best thing, a representation (picture, web page, whatever).

A picture of a rock is not an HTTP representation of the rock.

The HTTP definition of "representation" is far narrower than the
general English definition.

>> ...
>> If the resource is not web-accessible, then it should not be denoted
>> by a URI that is dereferencable -- or if it is dereferenced, nothing
>> should be returned.
> 
> I don't think the term "web-accessible" is well-defined but I think you
> seem to mean that "if a resource is other than a bag of bits that can be
> delivered over the web, then it should not be denoted by a URI that is
> dereferencable." But according to the HTTP specification, *no resource*
> is a bag of bits. Or at least Web clients have *no access* to the bag of
> bits that might be the internal site representation of the resource. All
> they have access to are representations, whether the resource is a rock,
> or a namespace, or a document or a database record.

Web applications do not have access to the actual resource, no, but
a representation of the resource is analogous to getting the actual
resource. For that to happen, the resource has to be digitally
encoded in some fashion.

A rock (at least for the moment) cannot be digitally encoded, and therefore
is not web-accessible.

A picture of a rock is not the rock. A prose description of a rock
is not the rock. Yet the picture, the description, and the rock all
may be separately denoted by URI.

If you use the same URI to denote the rock and the picture of the
rock, how do you say anything about either without ambiguity? You
can't.

>> ...
>> A schema is not a representation of a vocabulary. Sorry. Nope. It's
>> something that uses the terms of a vocabulary, but the vocabulary itself
>> is abstract, just as are the terms.
> 
> Why not?

A vocabulary is an abstract set of terms with associated semantics.

A schema is a document that describes vocabulary terms.

You don't see those as being different? I certainly do. This
is demonstrated by being able to describe the very same vocabulary
and terms using different languages/encodings, each of which
constitutes a distinct schema, and hence a distinct resource,
which may be denoted by their own URI.

And, e.g. an XML Schema does not define a vocabulary. It defines
a document model which uses one or more vocabularies to name
structural components of that document model. The vocabulary is
not tied to the schema. If that were so, then it would not have
been possible for there to be two DTD's for XHTML, Strict and
Frameset, which define different structure for the same vocabulary
term.

Which DTD/Schema equates to the vocabulary? Clearly, neither.

No, a vocabulary and schema are definitely not the same thing.

Regards,

Patrick

--
               
Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Wednesday, 3 July 2002 13:28:40 GMT

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