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Re: Inference in daml

From: Geoff Chappell <geoff@sover.net>
Date: Sun, 17 Jun 2001 20:14:58 -0400
Message-ID: <04cb01c0f78b$b5c86d60$835ec6d1@goat>
To: "Sean B. Palmer" <sean@mysterylights.com>
Cc: <www-archive@w3.org>

----- Original Message -----
From: "Sean B. Palmer" <sean@mysterylights.com>
To: "Geoff Chappell" <geoff@sover.net>
Cc: <www-archive@w3.org>
Sent: Sunday, June 17, 2001 8:59 PM
Subject: Re: Inference in daml

> Taking this off-list (actually, to www-archive) because my
> understanding is a bit murky from here on in...
Thanks for sticking with it.

> > But can't you make use of logical equivalents? i.e. "p->q" has
> > the same truth table as "q or not p" -- which can be expressed
> > in daml.
> But I think that once you go from "p->q" to "q or not p" which in DAML
> is more like "union of q and the compliment of p" as you have
> demonstrated, you can only rely on the semantics (i.e. rules,
> inferences) of DAML to provide the implications, because it lacks the
> terms required to become a full FOL language.

I guess that's what I'm trying to figure out - whether it really does lack
the terms required to become a full FOL language. If it has implication,
universal and existential quantification (via toClass and hasClass), boolean
operations and negation, can't it express FOL (albeit in a cumbersome
fashion)? (BTW, I don't know the answer to that question - either whether it
truly has those features or if they are sufficient to claim FOL-ness).

>DAML is there to provide
> a simple ontology framework, not to state the full range of inferences
> up front. It does howver provide you with enough terms to create
> simple statements from which many inference rules can be derived.
I understand that the primary intent of daml (at this point anyway) is not
to provide a basis for a full-fledged inference system. Whether the
designers intended it to be and whether it is are different questions.

> > The question is, if you express the rule in that form (by defining
> > a class of things that are q or not p and say that all things are
> > members of that class) will a processor that correctly interprets
> > the semantics of the daml language necessarily interpret the rule
> > as an implication?
> It should do, but in general RDF inference engines, you'll probably
> have to feed the rules in yourself, which is useful because
> practically you only want to come to one particular conclusion,
> although you could quite easily generate hundreds of others. The
> complication arises when you want one particular bit of information,
> but have to go through several different inferences to get there,
> which you don't care about (i.e. don't want on the output).

My interest really isn't in having a daml-speaking system be able to do
inference (though I think that by claiming to fully support daml such a
system would have to). I'm more interested in understanding if daml can
provide a firm semantic base for rule interchange between different systems.
So rules in prolog,datalog,etc can be serialized in daml and reliably,
predictably and without loss of meaning be deserialized by n3/cwm or some
other logic system. Not sure it would really make sense to do so - just
exploring the possibility...

> Once again, TimBL's log namespace, DAML, and RDF Schema make a
> powerful mix.
I haven't really played with it. I'm sure it does has the necessary
expressive power (when interpreted by a system that understands log
namespace). I'm just not clear where it's going - is it trying to become a
knowledge representation language or a logic system? is it anticipated that
n3 will become the interchange standard which all other logic systems must
speak? what's the relationship to the current rdf standards process? etc.

Received on Sunday, 17 June 2001 21:49:52 UTC

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