W3C home > Mailing lists > Public > www-rdf-interest@w3.org > November 2002

Re: a URI is a name (tel uri scheme and VCARD RDF)

From: Paul Prescod <paul@prescod.net>
Date: Sun, 24 Nov 2002 16:43:04 -0800
Message-ID: <3DE17218.80404@prescod.net>
To: Alexander Jerusalem <ajeru@vknn.org>, www-rdf-interest@w3.org

Alexander Jerusalem wrote:

> I'm not sure if the following is of any relevance for this thread but
> your discussion reminds me of a question I have always had regarding RDF:
> URIs, it seems to me, are used in two completely different ways: On 
> the  one hand they are just unique names for something. On the other 
> hand  they are used to point to something and provide a kind of 
> processing  instruction that allows us to physically retrieve the 
> thing it points to.

Yes, they are identifiers and locators. Identifiers first, locators second.

>  Now when we talk about someone's homepage for example, I don't think
> it is appropriate to use the URL that allows us to physically retrieve
> the homepage as the unique name of the homepage. The two roles should 
> be strictly separated. The reason is that I could have made a lot of
> statements about the homepage that use this URI as a unique name, that
> is as their subject. The physical address, however, can change.

If the address of the thing changes, then according to web 
infrastructure, it is basically a new thing that happens to have the 
same content as the old thing.

  * http://www.w3.org/Provider/Style/URI.html

The word "physical" is used in a funny way in computer science 
discussions. There is no such thing as a physical URI. They are all 
interpreted by server software so that there is no reason in principle 
to _ever_ change a URI except for limitations of implementation 
technology or effort.

Anyhow, why not use RDF to make the assertion that the new page is 
daml:equivalentTo the old one (or be more precise and say something like 
the new URI supercedes the old one).

> So even for internet resources, I think we should have one URI to name
> it and another one to point at it, even if the two happen to have the
> same sequence of characters at any one point in time.

Discussed here:


  Paul Prescod
Received on Sunday, 24 November 2002 19:43:37 UTC

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