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

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.

>  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.

> > But yes, the conclusion that "35" is an age of :margaret
> > isn't supported by simple entialment 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.

> > > > > 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.

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


> > 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.


> > Hmm... good question. Maybe it's been implicit all along.
> > Maybe it belongs in the RDF model theory spec, in
> > a discussion of... umm... 'extensions' to RDF,
> > as you call them.
> > 
> > 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.

Maybe this aspect of RDF is like that.


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

Received on Friday, 24 May 2002 22:34:28 UTC