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RE: Logic and Using The Semantic Web Toolbox

From: <jos.deroo.jd@belgium.agfa.com>
Date: Wed, 13 Dec 2000 15:52:20 +0100
To: " - *Ora.Lassila@nokia.com" <Ora.Lassila@nokia.com>
Cc: " - *www-rdf-logic@w3.org" <www-rdf-logic@w3.org>
Message-Id: <0006800037030168000002L082*@MHS>
Ora wrote in a reply to Pat:
> > Ah, I discern a ray of hope. Am I correct, then, in thinking
> > that by asserting a reified description of a triple (that is,
> > the four triples which describe it as being a triple plus
> > giving its three components), one is NOT thereby also
> > asserting the triple itself? That would greatly simplify the
> > semantics of RDF, certainly.
> Exactly! Asserting the reification is independent from asserting
> the triple itself. And only those statements we have asserted
> we consider as "facts".

Ok, maybe we are completely wrong (please tell us), but we see a
distinction between asserting
  <rdf:Statement>
    <rdf:subject>#cernDoc</rdf:subject>
    <rdf:predicate>#includes</rdf:predicate>
    <rdf:object>thisDocument</rdf:object>
  </rdf:Statement>

and asserting
  <rdf:Description>
    <rdf:type resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Statement"/>
    <rdf:subject resource="#cernDoc"/>
    <rdf:predicate resource="#includes"/>
    <rdf:object>thisDocument</rdf:object>
  </rdf:Description>

In the first ("assembly" RDF) representation the single statement
  [#cernDoc] #include [thisDocument]
is asserted and becomes a fact

In the second (reified RDF) representation the 4 statements
  [#genid] rdf:type [rdf:Statement]
  [#genid] rdf:subject [#cernDoc]
  [#genid] rdf:predicate [#includes]
  [#genid] rdf:object [thisDocument]
are asserted as 4 facts and indeed nothing is asserted about
the triple itself!

I know that the first representation is very confusing and
lengthy and not human readable and so on, but it is (I think)
valid RDF and it is a way to have "compound" subjects and objects
such as in http://www.agfa.com/w3c/euler/lists.axiom.rdf
without the need for reification.
Only the "outer" statements are asserted (as facts, Horn clauses,
etc) so a "nested" statement is not asserted at all.

--
Jos De Roo, AGFA
Received on Wednesday, 13 December 2000 09:53:09 GMT

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