Re: How to capture modeling information in WOL

From: Frank van Harmelen <Frank.van.Harmelen@cs.vu.nl>
Subject: Re: How to capture modeling information in WOL
Date: Sat, 29 Dec 2001 00:31:57 +0100

> Dieter wrote:
> 
> > > I recall many discussions on how to deal with modeling information in
> > > a logical framework. Lets take a simple example. A statement like
> > >
> > >       (1) a & b
> > >
> > > should be treaded completely equal to a statement
> > >
> > >       (2) b & a
> > >
> > > at a logical level. However, at a modeling level you may want to know
> > > whether a person wrote (1) or (2) because it may reflect the fact that
> > > b is more "important" to him.
> 
> Ian replied:
> 
> > On the web we often wont know who (or what) said what, or in what
> > order. Machine processing may mangle syntax. Users may have widely
> > divergent backgrounds and cultures. All these considerations (and
> > probably others) suggest that it would be dangerous to make
> > assumptions based purely on one interpretation of the meaning of a
> > given ordering.
> 
> Ian,
> 
> I agree with you that Dieter's examples were not very well chosen, but I
> think the point still stands: there are logically equivalent statements
> which carry a different "pragmatics", or "intention" or "modelling style"
> or whatever one wants to call it.  
> 
> Of course it is risky to write about this, because it is by definition
> soft fluffy stuff, but nevertheless quite important to many people
> (exclusing logicians, perhaps).  

Actually, logicians are precisely the people who care most about these
sorts of things.  You just have to look at all the light and heat
surrounding non-classical logics.  :-)

> Alternative examples could perhaps be:
> 
> - "a -> b" is equivalent to "~a V b" but I've seen many good modellers
> preferring one over the other in certain situations. The first says
> something like "whenever a is true, b must also be true", the second says
> something like "at least one of these two is true". (And yes, of course I
> know the truth-tables of FOL, but still).  
> 
> - "~(a & b)" is equivalent to "~a V ~b", but many people would prefer the
> first if they want to express a constraint to the effect that a and b
> cannot be true simultaneously. (and yes, I know that the 2nd form says
> that at least one of them must be false, so that's the same thing, but
> still. I'm observing, not defending).  

[...]

> Thus, I think it is very important that OWL does not only focus on
"logical equivalence" of statements (something that DAML+OIL has focussed
on exclusively), but that it is possible to capture something like the
"modelling style" or the "syntactic form" of logically equivalent
expressions.  

Certainly these sorts of things need to be addressed.  However, I think
that they need to be addressed in the context of a formal meaning for the
language.  

> (Yes, I know this is shakey grounds, non-monotonicity is lurking, etc, but still). 
> 
> (Actually, I don't think this is something that needs to be part of the
> language definition, but something that should be possible to be captured
> by tools such as editors. The language needs to give sufficient
> infrastructure for them to do this. DAML+OIL does not give sufficient
> infrastructure for this).  

Actually, it is not necessary for this infrastructure to be in the
semantic-bearing part of the ontology language at all.

> I'm not at all convinced that Dieter's proposal on using RDF-entailment
> for reasoning about the syntactic structure makes sense, but I would
> support the general desire to make such distinctions in some way or
> other.  

Sure.  There are lots of pragmatic issues involving the creation and
maintenance of collections of information.  However, without a firm syntax
and semantics, pragmatic issues get bogged down in misunderstandings.

> I would like to hear what others in the group think on this. 
> 
> Frank.
>    ----

peter

Received on Wednesday, 2 January 2002 10:49:54 UTC