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Re: A use case for anon nodes - action from telecon

From: pat hayes <phayes@ai.uwf.edu>
Date: Thu, 26 Jul 2001 12:19:18 -0700
Message-Id: <v04210102b78619fa6872@[]>
To: Graham Klyne <Graham.Klyne@Baltimore.com>
Cc: Brian McBride <bwm@hplb.hpl.hp.com>, w3c-rdfcore-wg@w3.org
>At 10:38 PM 7/23/01 -0700, pat hayes wrote:
>>>Graham Klyne wrote:
>>> > So where does this leave the original discussion?  I think we still have
>>> > every anonymous resource being something whose existence is asserted.
>>>Winding back the stack, (is the data still there?) you objected to the
>>>use case on the grounds that it represented a query template and was thus
>>>not sanctioned by M&S.
>>>I think we've got to the point where this is a legitimate use case.  Yes?
>>I don't think so. At the least, we should put this up as an 
>>explicit item for discussion: do we have a clear notion of query, 
>>and how does it relate to the notion of an assertion? (What does it 
>>mean to satisfy a query, can queries generate other queries, can 
>>queries be incorporated into an RDf graph (how?), can one query a 
>>literal, and so on.)
>Brian eventually convinced me that his example was NOT a query.

He hasn't convinced me yet. Look, its a simple point. The scenario 
involves two agents posting pieces of RDF and someone noticing a 
relationship between those pieces of RDF which triggers some kind of 
commercial transaction.  What is that relationship? If it is that one 
of them entails the other, then the one that is entailed by the other 
was a query, in the required sense. (If it isn't an entailment, what 
is it?)

>I could be wrong, but you may have been making the same assumption 
>that I made, namely that the description of the buyer service 
>asserted the existence of that which was to be purchased.  But on 
>closer examination, none of the existential variables in the 
>description actually stood for "roses":  ?x stood for the service, 
>and ?y stood for a concept of quantity constructed from a number and 
>a unit of weight.
>The statement:
>    ?x product Roses .
>was not saying that ?x was an instance of the product roses;  ?x was 
>the service, and the above statement was a description of the 
>service.  I think the implied meaning to an English speaker would 
>have been clearer if the statement were written as:
>    ?x offeredForSaleOrPurchase Roses .

I think this example has been valuable because it illustrates a much 
bigger and more important point than the one we started with. The 
implied meaning to an English speaker is *completely irrelevant* 
here. RDF is supposed to be used by software agents, not English 
speakers (if we could rely on the native savvy of English speakers, 
we could do it all in HTML). So the only content that any piece of 
RDF (or DAML, or KIF, or any of these 'formal' languages for 
capturing content) actually contains is what some mechanical agent 
could infer from it (together with whatever other pieces of RDF it is 
able to glean from various sources, of course.)

If you apply that criterion to Brian's example, and if you take it to 
be an assertion, then all that you could possibly infer is that four 
things exist and a few relations are true between them. If this is 
supposed to convey the fact that one of these things is a 'service' 
and therefore that it implies that a lot of other things exist (eg 
batches of roses which are available for sale or purchase -I've lost 
track of whether we are selling them or buying them), then something 
needs to say that.  Nothing in Brian's example seems to say that, 
however, so there is no basis for anything to be able to conclude it. 
(I would hazard a guess that the only way to say what needs to be 
said here is to use a universal quantifier, by the way.)

Pat Hayes

(650)859 6569 w
(650)494 3973 h (until September)
Received on Thursday, 26 July 2001 15:19:10 UTC

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