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RE: What is an RDF Query?

From: Peter F. Patel-Schneider <pfps@research.bell-labs.com>
Date: Sun, 16 Sep 2001 21:41:59 -0400
To: G.R.Wagner@tm.tue.nl
Cc: www-rdf-rules@w3.org
Message-Id: <20010916214159B.pfps@research.bell-labs.com>
From: "Wagner, G.R." <G.R.Wagner@tm.tue.nl>
Subject: RE: What is an RDF Query?
Date: Sun, 16 Sep 2001 23:28:33 +0200

> >> 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.

Yes, sure, but this query language is not necessarily the same language as
that use for antecedants of rules.

> Both with respect to bottom-up and to top-down evaluation 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.

Not to me it isn't.  Again, there are lots of things in query languages
(like SQL) that we may not want in antecedants of rules.  Similarly, there
may be things in rule consequents (e.g., variables) that we may not want in
the assertion language.

> Gerd Wagner
> Eindhoven Univ. of Technology

Peter F. Patel-Schneider
Received on Sunday, 16 September 2001 21:43:44 GMT

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