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Question regarding open vs closed formulas (n3)

From: Seth Ladd <seth@brivo.net>
Date: 25 Jun 2003 16:22:09 -0400
To: www-rdf-rules@w3.org
Message-Id: <1056572529.1597.186.camel@localhost>


If the outer most formula in cwm is open (which I'm assuming because I'm
able to add triples to it), how can a inner formula, such as {:seth :has
?X} => {:seth :likes :?x}, ever return (that is, find the set of paths
that match :seth :has ?X)?

How can it, theoretically, ever know it's gotten all the results for the
query, and therefore, ever do the log:implies? In an open world, the
query :seth :has ?x can't be proven to return all the matches, can it?

If so, does that mean the world is closed for just a moment?

I'm having a hard time writing a solution to this use case: I want to
buy a Jimmy Buffet CD for Bob, one he doesn't have, and it's under $10
dollars. Steve and Justin know what Bob has, so ask them. Ask Amazon
then for prices.  It's the "CDs that Bob /doesn't/ own" that I'm having
difficulty with. I'm worked out a owl:complementOf rules, but it's the
act of computing the rdf:List of CDs Bob owns that gets me. I'm not sure
if I can compute that List (or merge two Lists).

If I found a pre-existing List of CDs Bob owned, I could easily find
those that he does NOT own.  But if I only find the facts that :Bob
:owns :CD1. :Bob :owns :CD2, then I haven't been able to turn those two
facts into a rdf:List (using n3's rules).

Maybe the question I should be asking is: Is this possible?  It would
seem like the above use case is valid, and given a few facts on the
network about what CDs Bob owns, I should be able to infer what he
doesn't own.

Any ideas or tips?

Thanks very much,
Received on Wednesday, 25 June 2003 16:22:15 UTC

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