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Re: comments on Web Architecture First Edition

From: Dan Brickley <danbri@w3.org>
Date: Sat, 08 May 2004 21:01:09 +0100
Message-ID: <409D3C85.4040300@w3.org>
To: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Cc: Pat Hayes <phayes@ihmc.us>, "Roy T. Fielding" <fielding@gbiv.com>, public-webarch-comments@w3.org, w3c-rdfcore-wg@w3.org

Jeremy Carroll wrote:

> 
> 
> A very minor point:
> 
> Pat Hayes wrote:
> 
>> It seems to identify 'access' with 'identify', for example where it says
>>
>> "A URI must be assigned to a resource in order for agents to be able 
>> to refer to the resource. It follows that a resource should be 
>> assigned a URI if a third party might reasonably want to link to it, 
>> make or refute assertions about it, retrieve or cache a representation 
>> of it, include all or part of it by reference into another 
>> representation, annotate it, or perform other operations on it."
>>
> 
> The quoted paragraph is untrue (the word "must").
> OWL permits reference to uniquely identified resources without them 
> having a URI. (through the use of functional and inverse functional 
> properties)
> Suggest a minimal rewording of insert "easily"
> i.e.
> "A URI must be assigned to a resource in order for agents to be able to
>  easily refer to the resource. It follows that a resource should be 
> assigned a  URI if a third party might reasonably want to link to it, 
> make or refute assertions about it, retrieve or cache a representation 
> of it, include  all or part of it by reference into another 
> representation, annotate it, or perform other operations on it."
> 
> Although my preference would be to take Pat's comments seriously which 
> may require greater rewording.
> 
> 
> 
>>> Where does it say that all resources have a unique identifier?
>>
>> Sorry about that last one, I phrased it badly. I know the document 
>> does not say that resources have a unique URI, ie that URIs cannot 
>> converge in identification; in fact it explicitly denies it. What I 
>> should have said is that the idea that resources must be identified by 
>> an unambiguous URI has no rational basis, etc.. As I have explained in 
>> earlier emails, with examples, it is not necessary to have an 
>> identifier for something in order to refer to it.
> 
> 
> OWL's use of Functional and InverseFunctional Properties is a simple 
> example of this, I can flesh this out if it is helpful.

Yes, it would be good for the doc to be clear on this. The notion that 
we can  only refer to things that have URIs has had it's day. The use of 
reference by description (using RDF/OWL identity reasoning) is an 
important aspect of many present-day RDF systems, and not some academic 
corner case.

cheers,

Dan
Received on Saturday, 8 May 2004 16:01:12 EDT

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