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Re: semantics status of RDF(S)

From: Graham Klyne <GK@ninebynine.org>
Date: Fri, 06 Apr 2001 14:11:48 +0100
Message-Id: <5.0.2.1.2.20010404172601.03c53ec0@joy.songbird.com>
To: Aaron Swartz <aswartz@swartzfam.com>
Cc: RDF Logic <www-rdf-logic@w3.org>
At 06:36 PM 4/3/01 -0500, Aaron Swartz wrote:
>... reification. Saying negation, truth,
>etc. works just fine in RDF. Simply reify. Here's how it would be in XRDF:
>
><rdf:Description>
>   <negation rdf:resource="#s"
></rdf:Description>
>
><rdf:Description rdf:about="#s">
>   <rdf:subject rdf:resource="mailto:pfps@research.bell-labs.com" />
>   <rdf:predicate rdf:resource="http://example.org/confusedAbout" />
>   <rdf:object>reification</rdf:object>
></rdf:Description>
>
>Or in English:
>
>The thing that is the negation of the triple
>{mailto:pfps@research.bell-labs.com confusedAbout "reification}.
>
>I think N3 does it like this:
>
>[ :negation
>     { <mailto:pfps@research.bell-labs.com> :confusedAbout "reification" .}
>]

Hmmm... what happens if one tries to negate an assertion required for 
reification?

Imagine some statement:

   (p a b)

Its reification:

   (s1 rdf:type rdf:Statement)
   (s1 rdf:property p)
   (s1 rdf:subject s)
   (s1 rdf:object s)

Now assert s1 is not a statement:

   (s1t rdf:type rdf:Statement)
   (s1t rdf:property rdf:Type)
   (s1t rdf:subject s1)
   (s1t rdf:object rdf:Statement)

   (s1ns :negation s1t)

Now, it seems to me, that attempting to express the negation of the 
original statement leads (at a minimum) to a potential confusion:

   (s1n :negation s1)

as one of the statements required for s1 to be a reification of s has been 
negated.

...

In the above, I've had to make some uncomfortable assumptions about how 
:negation would work.  As offered, it expresses a relation between some 
resource and the statement whose negation is being described.

(This wasn't immediately clear in the N3 originally offered, as the other 
statement was implicit in the notation.  What _is_ the statement triple

   (neg :negation pos)

to mean?)

I think I'm beginning to see the logical problems that have been mentioned, 
but I don't have a strong enough grounding in logical fundamentals to work 
my way through this just now.

#g


------------
Graham Klyne
GK@NineByNine.org
Received on Friday, 6 April 2001 11:29:53 GMT

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