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Re: RDF namespace conventions

From: Tim Berners-Lee <timbl@w3.org>
Date: Mon, 22 May 2000 11:51:55 -0400
Message-ID: <002801bfc405$a8742dd0$2a7b0a0a@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: Sunday, May 21, 2000 10:47 AM
Subject: Re: RDF namespace conventions


>At 09:16 AM 5/21/00 -0400, Tim Berners-Lee wrote:
>>>You are not prohibited from doing it, but you are `prohibited' from
>>>using dereferencing to schema as use cases for changing the spec.
>>>That is, you should firstly consider the use cases that _are_ a goal.
>>
>>
>>I'm sorry, but if the spec (and attendant expert interpretation)
>>disallows dereferncing of the URI, then prohibting chnaging the spec
>>on those grounds effectively prohibits dereferencing URIs.
>>(was this an accident or a slick process play by an anti-URI group?)
>>
>>What do we do with the use cases which are prohibited, I wonder.
>
>I don't think most of the proposals I've seen recently (my own status quo
>for instance) _prohibit_ this behavior by layers _above_ the namespace
>processor itself.
>
>If RDF wants to dereference a URI in a layer above the namespace processor,
>I don't think anyone will have any problem with that.

Good.  I had interpreted David Megginsons's message
http://lists.w3.org/Archives/Public/xml-uri/2000May/0210.html
as prohibiting that, as it was pretty explicit. All the people who
suggest using the schema-location attribute seem to be arguing
that way too. But I shall assume you are right until I hear otherwise: that
it is OK for an
upper layer to dreference the namespace name if it can.

> On the other hand, I
>think people will be thoroughly irritated to be told that Namespaces URIs
>necessarily should point to anything.


I have heard no one suggest that it should be made mandatory, or even that
a dereferancable URI scheme be mandatory.  (I have only heard it suggested
as a false argument by "exaggeration to absurdity".)

>I think you're going well past the main flow of the conversation by
>suggesting that 'prohibition' is on the table. Such a situation might
>appear were the Namespaces Rec officially reopened and the discussion
>turned to whether relative URLs or even URLs should be outright banned, but
>I don't see that here.
>
>The needs of the top layer don't necessarily determine the needs of a lower
>layer.


That is true only to a certain extent.  One of things which does have to be
consistent
is identity.  You can't combine a tokenizer and a parser if they have no
common
notion about the idenity of a token, thing passed between them.

In this case the only problem is with relative URIs.  (For use-case in which
the system breaks with relative URIs and literal comparison see
http://lists.w3.org/Archives/Public/xml-uri/2000May/0281.html
)

So, the layer separation you suggest would work only with either
(a) no relative URIs -- at least a warning that XML lower layers don't grok
them, or
(b) change lower layers to absolutize before comparing.

Either of these would be consistent.  The second would be cleaner.

>Simon St.Laurent


Tim BL
Received on Monday, 22 May 2000 11:50:05 UTC

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