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Re: Implementing statement grouping, contexts, quads and scopes

From: Alberto Reggiori <areggiori@webweaving.org>
Date: Mon, 24 Jun 2002 19:48:31 +0200
Message-ID: <3D175B6E.7712D5FF@webweaving.org>
To: Jonathan Borden <jonathan@openhealth.org>
CC: RDF Interest <www-rdf-interest@w3.org>, RDF Logic <www-rdf-logic@w3.org>
Jonathan Borden wrote:

> Don't you see what you are trying to do?

I think I can see what I am trying to do here, which is proposing a practical
solution (like Patrick I guess) to layer new semantics on top of RDF using
reification and the current XML/RDF syntax which most parsers understand
already :-)

Isn't the WebOnt supposed to layer OWL on top of RDF  using the XML/RDF _as it
is today_  [1] or am I missing something here ? :-)

Can somebody better explain to me what's wrong about using reification for
layering ?

> You are writing an N3 formula _which is not RDF but as if it were something
> in RDF_ and casually tossing this out as a solution to some problem _in
> OWL_.

well, you are right saying that the syntax is ugly, baroque and obese but it is
definitively valid XML/RDF :-)

> How is OWL to use such a formula if OWL is to be layered on RDF? How are
> such rules supposed to be specified? Sure if we accept N3 this is no problem
> but that's the point: N3 formulas, when represented as triples, use
> collections of unasserted triples. This is most basic:
>
> X=> Y
>
> does not imply (i.e. assert) X so you need a way to _say_ "X" without
> asserting X.

picking up bit and pieces from my previous example, I can define N3 formula X
as follow:

<rdf:Statement rdf:bagID="X">
   <rdf:subject rdf:resource="&ex;s" />
   <rdf:predicate rdf:resource="&ex;p" />
   <rdf:object rdf:resource="&ex;o" />
</rdf:Statement>
<owl:OWLPredicate rdf:about="&ex;p" rdf:bagID="#X"/>

which does *not* assert (s,p,o) in formula X while

<rdf:Description rdf:about="&ex;s"
                 rdf:bagID="Y">
   <ex:p rdf:resource="&ex;o" />
</rdf:Description>

*does* asserts (s,p,o) in formula (context) Y

where X=>Y becomes

<rdf:Description rdf:about="#X">
   <log:imples rdf:resource="#Y"/>
</rdf:Description>

which is ugly, but if you feed the above into the W3C RDF validator, you get
what you expect i.e. X=>Y in triples :)

> But hold on and understand this:
>
> You are proposing RDF reification as a way to 'implement' unasserted triples
> but you are using _another_ mechanism of unasserted triples in order to
> 'implement' reification. It is exactly these sorts of arguments that are
> akin to trying to develop a perpetual motion machine.

you might be right here, but I find that the mixture of the two mechanisms
working nicely together :)

> So certainly if you give us a mechanism for N3 formulae the problem would be
> solved. That is the whole point, really.

I am not up to speed enough with N3 and rule based systems to say that this is
the solution to layering, but I can definitely say that this is *a* solution
(or not)

regards

Alberto

[1] http://lists.w3.org/Archives/Public/www-rdf-interest/2002Jun/0211.html
Received on Monday, 24 June 2002 13:42:01 GMT

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