W3C home > Mailing lists > Public > www-rdf-logic@w3.org > June 2002

Re: Implementing statement grouping, contexts, quads and scopes

From: pat hayes <phayes@ai.uwf.edu>
Date: Tue, 25 Jun 2002 11:46:48 -0500
Message-Id: <p05111b0db93e4be82f5f@[]>
To: areggiori@webweaving.org
Cc: 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
>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" />
><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" />
>*does* asserts (s,p,o) in formula (context) Y
>where X=>Y becomes
><rdf:Description rdf:about="#X">
>    <log:imples rdf:resource="#Y"/>
>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 :)

Well that is very remarkable, since there is no valid way to express 
an implication in RDF triples. log:implies is meaningless in RDF(S), 
please bear in mind.

>>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)

I can definitely say that it is not. Next question?

Pat Hayes

IHMC					(850)434 8903   home
40 South Alcaniz St.			(850)202 4416   office
Pensacola,  FL 32501			(850)202 4440   fax
Received on Tuesday, 25 June 2002 12:46:51 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 6 January 2015 21:38:24 UTC