Re: MISC: Internet Media Type registration: proposed TAG finding

From: Dan Connolly <connolly@w3.org>
Subject: Re: MISC: Internet Media Type registration: proposed TAG finding
Date: 24 May 2002 21:34:31 -0500

> On Fri, 2002-05-24 at 19:09, Peter F. Patel-Schneider wrote:
> > From: Dan Connolly <connolly@w3.org>
> > Subject: Re: MISC: Internet Media Type registration: proposed TAG finding
> > Date: 24 May 2002 16:13:32 -0500
> [...]
> > > The author of the best-friend document, by choosing to use
> > > ont:UniqueProperty class, licensed inferences
> > > based on the specification of that class. The conclusion
> > > that "35" is an :age of :margaret is supported
> > > by the DAML+OIL spec.
> > 
> > Yes, but not by the RDF spec, and any agent has no business labelling
> > anything as RDF inferences that are not sanctioned by the RDF model theory.
> 
> Hmm... that's one way to think of 'RDF inferences'.
> It's not one that appeals to me.
> 
> > > I can think of two agents (cwm and Euler) that
> > > do a lot more than simple entailment, when
> > > asked to. I think of them as RDF agents.
> > 
> > They are not.
> 
> Er... I accept that as your opinion.
> I disagree.

Then it is up to you to show how the RDF specification admits cwm and Euler
as RDF agents.  I claim that they are not, and back up my claim by your
statement that cwm and Euler do more than is santioned by the RDF model
theory. 

> >  If they label their entailments as RDF entailment then they
> > are being deceitful, moreover.
> 
> They don't label their entailments as RDF simple entailment.
> They only make conclusions that they're asked to make;
> you have to tell Euler and cwm to include axioms
> about DAML+OIL in order for them to make these
> conclusions. There's nothing deceitful going on.

Anyone who labels the results as valid RDF consequences is incorrect, and
if they know that they should know, is being deceitful.  Anyone who calls
the results RDF is verging on deceit.

> > > But yes, the conclusion that "35" is an age of :margaret
> > > isn't supported by simple entailment alone, and
> > > justification of that conclusion needs to be clear
> > > about including the DAML+OIL spec.
> > 
> > How can this be done in RDF?  It cannot.
> 
> I disagree.
> 
> If you had some argument beyond
> assertion, we might productively discuss it further.

Well, there is no way in the RDF model theory to entail that two different
URIrefs denote the same resource.  The DAML+OIL meaning of UniqueProperty
(or whatever the name for making a property be functional is) can be used
to DAML+OIL-entail that two different URIrefs denote the same resource.
QED

> > > > > > Sure, but the non-understood part may completely change the meaning of the
> > > > > > other part,
> > > > > 
> > > > > No, I don't think so...
> > > > 
> > > > Why not?  What about 
> > > > 
> > > > 	<fol:negation>
> > > > 	  <fol:statement>
> > > > 	    <rdf:Person rdf:about="#John">
> > > > 	      <loves rdf:resource="#Mary">
> > > > 	    </rdf:Person>
> > > > 	  </fol:statement>
> > > > 	</fol:negation>
> > > 
> > > I'm not sure how to parse that. If I presume that fol:negation
> > > is an RDF typednode, and convert to (something close to) KIF, I get:
> > > 
> > >   (exists (?n)
> > >     (rdf:type ?n fol:negation)
> > >     (fol:statement ?n #John)
> > >     (rdf:type #John rdf:Person)
> > >     (loves #John #Mary)
> > >   )
> > > 
> > > so... ?n is a negation, and it's somehow related to John.
> > > I think you meant to express something like
> > >   (not (loves John Mary))
> > 
> > That is indeed what I meant. I expressed it in RDF syntax, which according
> > to you, should be perfectly fine.  I used my extension to RDF reasoning,
> > which, according to you, should also be perfectly fine.
> 
> I can't make sense of this extension. Maybe you could explain
> how it works a little more generally than this one example.
> I don't understand how the fol:negation class's specification
> reaches out thru #John to the (loves #John #Mary) triple.

But according to your rules, any method of providing meaning for this
extension is adequate.  OK, the method that I will use is that it means
what I mean it to mean.  

This is no harder for an RDF-only agent to understand than the DMAL+OIL
meaning of daml:UnambiguousProperty.

> In particular, I don't understand it well enough to
> see if it's non-monotonic.

Why should this be a problem?

> > > but that's really awkward to do in RDF, but I suppose
> > > it could look like:
> > > 
> > >   <fol:Negation>
> > >     <fol:predicateSymbol>http:...#loves</fol:predicateSymbol>
> > >     <fol:subjectSymbol>http:...#John</fol:predicateSymbol>
> > >     <fol:objectSymbol>http:...#loves</fol:objectSymbol>
> > >   </fol:Negation>
> > > 
> > > where fol:Negation is specified ala:
> > > 
> > >   (forall (?n ?s ?p ?o)
> > >     (<=>
> > >       (and
> > >         (predicateSymbol ?n ?p)
> > >         (subjectSymbol ?n ?s)
> > >         (objectSymbol ?n ?o)
> > >         (wtr
> > >            '(not (holds `(str->sym ?p) `(str->sym ?s) `(str->sym ?o))) )
> > >       )
> > >       (rdf:type ?n fol:Negation)
> > >   )
> > > 
> > > But even in that case, I *only* eliminate models when I
> > > learn the meaning of fol:Negation (i.e. when I add that axiom).
> > 
> > Yes, and this is no longer RDF.
> 
> I accept that as your opinion. I disagree.
> Argument by assertion is really no fun.

Well, how could it be RDF?  It doesn't match any syntax for RDF.  QED


[...]

> > > I suppose I'll send a comment to www-rdf-comments.
> > 
> > Go ahead, but where in the RDF specification is this *now* specified?  If
> > it is not there, then you have no business assuming it.
> 
> Some things seem like common sense the first time you write
> a spec. Nobody wrote "don't flood the network with zillions
> of inessential packets" in the IP spec. But it's implicitly in
> there, and all the designers, implelementors, and users have
> lots of business in assuming it.

Well, lots of others have become famous (or infamous) by exploiting this
loophole in the IP spec.  One can complain that they are not good IP
citizens, but they *are* abiding by the IP spec.  Similarly, lots of other
attacks on the net exploit holes in the specs for the net.

> Maybe this aspect of RDF is like that.

Sure, a hole that could be fixed, but, for now, a hole that can be
exploited.

> -- 
> Dan Connolly, W3C http://www.w3.org/People/Connolly/
> 

peter

Received on Saturday, 25 May 2002 00:05:18 UTC