W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > September 2001

Re: What is an RDF Query?

From: Pat Hayes <phayes@ai.uwf.edu>
Date: Wed, 19 Sep 2001 11:54:58 -0500
Message-Id: <p05101015b7ce7ded5bc7@[]>
To: Brian McBride <bwm@hplb.hpl.hp.com>
Cc: w3c-rdfcore-wg@w3.org
>Please don't crosspost mail to rdf-core.  w3c-rdf-core is a WG
>only mailing list.
>I guess you didn't cross post, but you have kinda invited your
>correspondent to post to this list and I'm not sure why.
>This looks like a conversation to have on the rules list.  You
>can always draw the WG attention to it, for those interested.

Whoops, sorry, that was a mailing typo. I will redefine my email 
nicknames: rdfc and rdfr are too similar, obviously.


>Pat Hayes wrote:
>>>[freed from spam trap -rrs]
>>>Date: Sun, 16 Sep 2001 17:28:51 -0400 (EDT)
>>>Message-ID: <511BB18E82E9D11188230008C724064602D9DDAC@tmex1.tm.tue.nl>
>>>From: "Wagner, G.R." <G.R.Wagner@tm.tue.nl>
>>>To: "'Peter F. Patel-Schneider '" <pfps@research.bell-labs.com>,
>>>         "'eric@w3.org '" <eric@w3.org>
>>>Cc: "'www-rdf-rules@w3.org '" <www-rdf-rules@w3.org>
>>>>>  Thanks for the clarification. I propose that we use a term for the
>>>>>  antecedent that is NOT "assertion". Furthur, I propose that this term
>>>>>  either be "query" or that the definition express the commonality with
>>>>>  queries.
>>>>  I propose that we do not do this.  I oppose calling the antecedant of a
>>>>  rule anything other than the antecedant of a rule!
>>>It's not a matter of how you call it, but what form it may
>>>have, or, in other words, from which language it comes.
>>>Obviously, any practical KR system, such as Prolog, relational
>>>databases, or RDF, has an assertion (or input) language defining
>>>the admissible (logical) expressions that may be asserted/inserted
>>>into a KB, and it has a query language defining the admissible
>>>expressions for querying/retrieving knowledge.
>>Sorry, but I don't find  that at all obvious, particularly if it is 
>>supposed to imply that these must be different languages.  And it 
>>IS a matter of how you call it; we are having a debate here about 
>>proper terminology. Such discussions do matter, since enormous 
>>amounts of time can be wasted in an interdisciplinary discussion by 
>>inadvertant clashes of terminology. For example:
>>>Both with respect to bottom-up and to top-down evaluation
>>These terms 'bottom-up' and 'top-down' are meaningless to me, I'm 
>>afraid. Apparently they are based on some kind of vertical analogy, 
>>but I don't know which way up the paper is supposed to be; I tend 
>>to think from left to right, forwards and backwards.
>>>it is
>>>natural then to define a derivation rule for a specific KR system
>>>in such a way that its antecedant is a query expression and its
>>>consequent is an input expression.
>>I have no idea what 'query expression' and 'input expression' mean 
>>here. In my terminology, a query expression would be one which was 
>>used for querying, so it presumably couldn't possibly be *part* of 
>>a rule (though it might match a part of a rule).
>>My basic point is that the functional roles of expressions and 
>>parts of expressions in an inference or rule-manipulating system 
>>should not be identified with their syntactic or logical 
>>descriptions, since the same structure, with the same logical 
>>meaning, can often be used for different functional purposes in 
>>different contexts. More generally, it is mistake to identify 
>>logical or assertional meaning with any particular kind of 
>>processing; the basic utility of logical analyses of meaning is 
>>that they allow different computational strategies to co-exist. So 
>>I want us not to adopt terminology which makes such identifications 
>>Pat Hayes

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Received on Wednesday, 19 September 2001 12:55:02 UTC

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