W3C home > Mailing lists > Public > xml-uri@w3.org > May 2000

Re: which layer for URI processing?

From: Tim Berners-Lee <timbl@w3.org>
Date: Wed, 24 May 2000 14:02:54 -0400
Message-ID: <010101bfc5aa$4bdb03e0$74eb5c8b@ridge.w3.org>
To: <xml-uri@w3.org>, "Simon St.Laurent" <simonstl@simonstl.com>

-----Original Message-----
From: Simon St.Laurent <simonstl@simonstl.com>
To: xml-uri@w3.org <xml-uri@w3.org>
Date: Wednesday, May 24, 2000 1:34 PM
Subject: which layer for URI processing?


>At 01:00 PM 5/24/00 -0400, Tim Berners-Lee wrote:
>>We disagree about which we would prefer. We are in the awkward
>>situation that we have all arrived in a situation that the URI spec
>>and the Namespace space are basically in conflict, which no one
>>likes. We need to get out of that situation.
>>
>>[...]
>>
>>So, while  I would not brand you, Tim, as anti-URI, somehow
>>we have to get a solution which is consistent with the URI spec.
>
>'Consistent with the URI spec' and 'consistent with the use of URIs in
>Namespaces in XML' - which is strictly as names - seem to be thoroughly
>incompatible, at least from your viewpoint.


Yes.

>I'd appreciate it if you could explain why you it is so critical that lower
>layers of processing handle the considerable amount of effort involved in


This is *NOT* a considerable amount of effort, this is calling a
simple well-defined string function which takes two string parameters
and returns one string value.

>treating URIs _as URIs_ rather than as strings for purposes of comparison,
>and why higher layers (like RDF and other models) can't be trusted with
>that responsibility.
>
>In short, explain your side of:
>SSL> I keep requesting that semantics be treated as a layer on top of
syntax,
>SSL> while you and Dan seem to be insisting that URI semantics be driven as
>SSL> deeply into the syntax layer as possible.


I have explianed this in a number of messages, but I accept that I
see as an explanation may not address our misunderstanding.
But please try to follow it.

My long "Database example .." was a worked example in some detail.
http://lists.w3.org/Archives/Public/xml-uri/2000May/0281.html
Here goes with a shorter one.

XSLT uses XPath which is included, I understand in the "lower layer" in your
scenario.
[If not, then what is?]
Supose I use XSLT to filter a document to ensure it doesn't have
any of an http://example.com/detonator namespace in it, because processing
this
would allow the document to destroy the chemical plant.
The XSLT sees "/detonator" in an incoming document
http://example.com/doc.xml
but it does not notice it as it does not absolutize it. The checked result
is
passed to the main control system. However, when
this "upper layer" runs it absolutizes it to find out what in upper layer
terms it really means, and
instantiates a chemical plant handler to handle the http://example.com/foo.
Bang.

Is this or is this not a problem?

I wouldn't be sitting here plowing though all this mail if I didn't htink it
was.

You can do different consistent things betwen different layers but you
cannot mess with identity of things common to both layers.

>Simon St.Laurent


Tim BL
Received on Wednesday, 24 May 2000 14:01:14 UTC

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