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Re: yet another non-entailment

From: Jeremy Carroll <jjc@hplb.hpl.hp.com>
Date: Tue, 27 Aug 2002 13:50:33 +0200
To: <www-webont-wg@w3.org>
Message-ID: <MABBLGKMPIJFCKFGDBEPGEBHCBAA.jjc@hplb.hpl.hp.com>

> This message brings up an interesting point about entailments.

> Why should I, or Jeremy, or the working group, approve of or disapprove of
> a particular entailment?

> My stance is clear.  I approve of exactly the entailments that follow from
> the model theory.

My view, which I think is largely in line with this, is that the entailment
tests and the model theory are two sides of the same coin.

Clearly if we approve tests which do not follow from the model theory then
before we are finished we either need to revisit the tests or to revisit the
model theory.

I feel that the tests provide clarity by making it clear to the non-expert
some of the consequences of the model theory. In RDF Core, where in truth,
only Pat is expert in model theory, this has been a very helpful feature of
entailment tests.

Thus if an entailment followed from the model theory that the WG did not
feel confortable with then this was an indication to Pat to go back and
tweak the model theory; or alternatively to argue why some or other feature
of the model theory was sufficiently desirable to merit a test that did not
accord with the groups intuitions.

Thus, at the moment there seems to be some discussion about the merits or
not of Pat's articulation of the model theory versus Peter's. Both Peter and
I have expressed this discussion by providing concrete examples of
entailments that hold in Peter's world and don't hold in Pat's world. I
think this is a helpful concrete way of articulating the differences. These
are likely to be more accessible than discussion about domain of discourse
and non well found set theory.

When we make decisions about the tests there is a need to make them
coherently. The peicemeal nature of test case approval will result in some
mistakes that will need to be revisited. But this seems to be adequately
covered by the process. In the final stages of our work we can expect
implementations that fully implement our specs including the model theory.
If they do not pass all the tests then the tests themselves are faulty and
will need to be corrected.

> Jeremy's stance below appears to be that he will disapprove of entailments
> on their own.

I expect the group has enough expertise to either avoid the pitfalls, or to
climb out of any holes that we end up in. I see the tests as guiding the
model theory just as much as the model theory guiding the tests. Both will
need to be corrected.

Received on Tuesday, 27 August 2002 07:45:45 UTC

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