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Re: The lost meaning of the HTTP protocol in URIs

From: Tim Berners-Lee <timbl@w3.org>
Date: Sun, 14 Sep 2003 13:59:28 -0400
Cc: Public W3C <www-archive@w3.org>
To: Stefano Mazzocchi <stefano@apache.org>
Message-Id: <2F3F5845-E6DD-11D7-9E54-000393914268@w3.org>


On Saturday, Sep 13, 2003, at 15:56 US/Eastern, Stefano Mazzocchi wrote:

>
> From the current state of affairs, the web is based on URIs. From what 
> I see, this is unlikely to change and I'm cool with this, expecially 
> because URIs that are general enough to indicate anything, even 
> concepts that are not "locatable".

What do you mean by, "not locatable"?  There are things, like abstract 
concepts,
which may not be objects you find on the web, but they are things
which one describe.


> Then, please, tell me: if these concepts are not locatable, why are we 
> supposed to use the HTTP protocol to indicate them?
>
> I know, I know: in order to keep them unique using the domain name 
> facilities... but ask yourself why in hell a namespace URI such as
>
>  http://www.w3.org/1999/xslt
>

The XSLT namespace is in fact

http://www.w3.org/1999/XSL/Transform

An engineer who comes across a document which
uses that namespace can look it up, and get information
leading him or her to the XSTL specification.

This is useful.  So while a namespace seems like an abstract
concept, to actually refer to it by the name of something
which can be looked up is variable.

In the semantic web, information can be used not only be
a person, but by a machine. So while the concept
of "two-digit US state code" may be a an abstract property,
in fact one can find the list of them and the correlation with
various other properties.  This is powerful.


> is not
>
>  uri://w3.org/xslt/1.0
>
> where:
>
>  1) there is no misleading since the protocol clearly indicate its 
> "unlocatable" status

You presumably mean that no one should ever look up what the
owner of the name said about it.
You need the "urn:" prefix not "uri:".
But betware that many urn: subschemes are actually less useful
because they are waiting for some sort of lookup mechanism,
and to the extent they have such a mechanism, they become just clumsier
versions of http:

>  2) the domain-based uniqueness is maintained, no, improved, given 
> that virtualhosts are not considered meaningful (there is no location 
> taking place, just unique identification)

The difference is an attitude of mind, and a mode of use.
Think of what you would like from your "uri:" space above, and use http:
space like that.

Use them like names not like locations. They are not locations.

>  3) version numbers are used instead of years. this makes them much 
> easier to remember (you remember the version of the namespace you want 
> to associate your content with, not the year that version was 
> published [unless the year *is* the version, like in 
> win95/98/2000/2003, but it's not the case here])

That is a question of web site management.
The advantage of years is that in 100 years time, when someone
wants to reuse they string "xslt", they will not have a problem.

> Please, tell me why this hasn't been since day one, because I'm going 
> crazy on this.

Think of them as names.

> --
> Stefano.
Received on Sunday, 14 September 2003 13:59:16 GMT

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