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Re: Logic and Using The Semantic Web Toolbox

From: Pierre-Antoine CHAMPIN <champin@bat710.univ-lyon1.fr>
Date: Wed, 13 Dec 2000 17:07:17 +0100
Message-ID: <3A379EB5.DCCE18E@bat710.univ-lyon1.fr>
To: jos.deroo.jd@belgium.agfa.com
CC: " - *www-rdf-logic@w3.org" <www-rdf-logic@w3.org>
jos.deroo.jd@belgium.agfa.com wrote:
> 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

It depends...
If your first example uses some strawman syntax, you may be right.
If it uses the XML syntax from RDF M&S recommendation, then no !
This is not asserting the statement you say, but 4 statements,
as Dan Connolly pointed out in his response.

Hence, if, as I suspect, my first hypothesis is right (strawman syntax),
you should be very cautious in using that syntax
since it CAN be interpreted as the XML syntax, but very differently from what you want.

> 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!

That's definitely true -- in the recommended XML syntax.

> I know that the first representation is very confusing and
> lengthy and not human readable and so on,

at least, I find it much more regular than the recommended XML syntax :)

> 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.

Ouch ! I do not agree !
This is only syntactical sugar to hide the modelling of reification ;
at the model/abstract syntax/graph level, reification is always there, and still the same.
Anyway, I agree this is a handy syntax for reification-intensive uses.

  Pierre-Antoine

-- 
Sometimes I think the surest sign that intelligent life exists elsewhere in the
universe is that none of it has tried to contact us.
(Bill Watterson -- Calvin & Hobbes)
Received on Wednesday, 13 December 2000 11:08:06 GMT

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