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Re: question about imports

From: pat hayes <phayes@ai.uwf.edu>
Date: Fri, 6 Dec 2002 09:48:33 -0600
Message-Id: <p05111b01ba16719c98e6@[10.0.100.86]>
To: "Peter F. Patel-Schneider" <pfps@research.bell-labs.com>
Cc: www-webont-wg@w3.org

>From: pat hayes <phayes@ai.uwf.edu>
>Subject: Re: question about imports
>Date: Thu, 5 Dec 2002 19:28:41 -0600

snip

>  > >>  >
>>  >>  >>  These two documents have exactly the same
>>  >>  >>  meaning, right?
>>  >>  >
>>  >>  >No, because the second is missing a triple.
>>  >>
>>  >>  They are syntactically distinct, but I believe they are true in
>>  >>  exactly the same interpretations (?). Keeping the imports triple with
>>  >>  the imported graph is like saying P and P instead of P, right?
>>  >
>>  >Huh?  Are you thinking that this is a dark triple?
>>
>>  No, of course not. But the truth-conditions on owl:imports B are
>>  exactly the same as the truth conditions on the imports closure of B,
>>  right (??) If not, what *are* the truth conditions on owl:imports?
>
>Close, but there is no way that OWL can turn off the RDF interpretation of
>the triple, is there?  The imports closure conditions can only add to this
>base condition, at least as far as I can figure.

True, but I guess I was assuming, perhaps naively, that an assertion 
of an owl:imports triple was supposed to actually assert something 
itself.

>
>>  >  When did these come back?
>>  >
>>  >>  >>  And the first, but not the second, refers to another
>>  >>  >>  document.
>>  >>  >
>>  >>  >And they have different meaning (as n-triples documents).
>>  >>  >
>>  >>
>>  >>  In what does the difference reside?
>>  >
>>  >I thought that every triple made an assertion.
>>
>>  I never said otherwise. That is beside the point of my question. What
>>  assertion does the imports triple  (considered in isolation, a single
>>  triple) actually make, other than that imports closure be true?
>
>Just the same as any other triple, no?
>
>>  (And
>>  BTW, what is the subject of that triple, and how does it enter into
>>  the truth-conditions?)
>
>Well, this is one of the problems of using triples.  The current proposal
>is that the subject of the triple is unimportant

Unimportant or implicit? Surely saying that A imports B in C cannot 
have the same meaning as saying that A imports B in A.

>and is (conventially)
>written as "".
>
>>  >If this is no longer true,
>>  >then I'm going to have a pile of changes to make.
>>
>>  Not only is it true, one can say more: it asserts that the <s,o> pair
>>  is in the extension of the property. What are the semantic conditions
>>  on IEXT(I(owl:imports)) ?
>
>Well, the editor's draft of the OWL semantics treats owl:imports specially.
>For details see the draft.

Will do. But it had better not attempt to both say that it is a 
triple and also that it has a meaning incompatible with the above, as 
the RDF spec now uses RFC 2119 language when talking about this. So 
any asserted triple must satisfy an IEXT-style meaning.

Pat

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Received on Friday, 6 December 2002 10:48:36 GMT

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