Re: A Problem With The Semantics of DAML+OIL Restrictions

From: Richard Fikes <fikes@KSL.Stanford.EDU>
Subject: Re: A Problem With The Semantics of DAML+OIL Restrictions
Date: Tue, 03 Jul 2001 07:41:15 -0700

> 
> By the way, I think the model theoretic semantics suffers from the same
> problem as the axiomatic semantics in this matter.  That is, both of
> them seem to treat each constraint in a restriction as sufficient
> conditions for membership in the class.  The constraints need to be
> combined when there is more than one of them in a restriction.
> 
> Richard


Richard is correct.   There are ``problems'' with the model-theoretic
semantics when restrictions have ``multiple'' restrictions on them.
However, the problems really amount to a divergence between the intended
reading of a restriction with multiple ``restrictions'' on it (form the
conjunction of the ``restrictions'') and the specification in the
model-theoretic semantics (each ``restriction'' is independantly both
necessary and sufficient).

However, one way of solving the problem is to leave things are they are!
Any restriction that doesn't satisfy the ``one restriction'' property is
syntactically valid, but will cause severe semantic difficulties.  The
axiomatization and the model theoretic semantics could then stay the same.

I don't think that the intended reading is viable.  Richard pointed out
that the intended reading has this non-monotonic component---if you add
``restrictions'' to a restriction its extension changes non-monotonically.

pete