Re: Joint Committee Meeting tomorrow May 22

From: Peter F. Patel-Schneider (
Date: 05/22/01

I've been looking at Stefan's Layers document, and have a number of
questions about it.  Most of these have to do with undefined or
underdefined terms and phrases.  I have some suggestions on what needs to
be changed, but I would prefer to make a general plea for such documents:

	If anyone wants to make a language proposal, they should have a
	formal definition of the proposal.

I do not view this as too onerous, as there need not be a semantic document
for most things, as the current semantics can be used.  The formal document
thus boils down mostly to a firm definition of the syntax of the language.

My comments on Stefans proposal:

Level 0:  I have no problems with this, except that it is very
under-defined.  I think that we could easily provide a layer of DAML+OIL
that is essentially frames done right.

Level 1:  The terms ``simple class'' and ``simplified property
restriction'' are not defined.  This makes the proposal very hard to
evaluate.  Even with a very restrictive definition of these phrases I have
a very strong feeling that reasoning will be just as hard in this level as
in the entire language, as level 1 includes qualified number restrictions
and enumerations.

Unique Name Assumption:  We discussed this a lot.  I think that a UNA would
be very useful, but it needs to be carefully crafted so that no
non-monotonicity leaks into the formalism.


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