Re: [RIF] Reaction to the proposal by Boley, Kifer et al

From: Francois Bry <bry@ifi.lmu.de>
Subject: Re: [RIF] Reaction to the proposal by Boley, Kifer et al
Date: Wed, 03 May 2006 14:21:28 +0200

> Peter F. Patel-Schneider wrote:
> >
> >> This is based on a known logic: infinite Herbrand interpretations.
> >>     
> >
> > Reference, please.
> 
> I could maybe help in giving reference if I would understand what you
> are asking for.

A reference to logics based on infinite Herbrand intepretations that shows
how they relate to standard first-order logics.

> How existentially quantified expressions are evaluated in relational
> databases, in deductive databasesw, and in logic progreamming is
> well-known, could be seen as "folklore knowledge". My guess is that you
> have a precise question in mind -- that I do not know.

In logics where every "domain element" has a name, the substitution
interpretation of quantifiers is well known.  However, how does this relate
to logics where there is not necessarily a name for every domain element or
where there cannot be a name for every domain element?

> > I worry about situations like the following.  
> >
> > Suppose that there (only) are two constants, T and F, and (only) one
> > one-place function, N.  Does it then follow from the following two facts
> >
> > 	N(T) = F
> > 	N(F) = T
> >
> > that
> >
> > 	Ax Ey x = N(y)
> >
> >
> > [...]
> >   
> Not in logic programming, relational databases, and deductive databases
> that have function symbols but not full treatment of equality. Of
> course, a full treatment of equality can be considered/added.

The proposal has a treatment of equality.  I was expecting it to be a "full
treatment", so I didn't see that there was anything to consider/add.

> >>> I worry about the connection between the proposal and RDF and OWL.  I do
> >>> not view it as appropriate to relegate existing Semantic Web languages to
> >>> an add-on query interface.
> >>>       
> >> Why?
> >>     
> >
> > Because we are supposed to be working within the confines of the Semantic Web.
> 
> I share this worry. However, marrying logic programming and RDF is
> however surely feasible and challenging. Marrying logic programming and
> OWl in some way is also surely possible and challenging.
> > Is it really?  It instead seems to me to be much more like a ghetto.  In
> > particular, the proposal uses a ternary predicate for RDF triples,
> > divorcing RDF facts like ex:a rdf:type ex:b from a representation
> > as ex:b(ex:a).
> >   
> To the best of my understanding, the one and the other syntax are both
> possible. Personally, I would prefer a syntax (subject predicate object)
> because it is natural and simple.

Is this a (single) ternary predicate?  If not, how does it match the
proposal?  If so, how can it be considered to be natural?

> I agree that integrating RDF/OWL through queries pose more problems than
> it might first seem.

Well many of these issues have already been brought up in discussions
within the working group, so it is not as if they are somehow invisible.

> François

Peter F. Patel-Schneider

Received on Wednesday, 3 May 2006 12:54:28 UTC