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Re: UPDATE: longer version of layering document

From: Jos De_Roo <jos.deroo.jd@belgium.agfa.com>
Date: Sat, 9 Feb 2002 11:03:34 +0100
To: pfps@research.bell-labs.com
Cc: "connolly" <connolly@w3.org>, "www-webont-wg" <www-webont-wg@w3.org>
Message-ID: <OF01895410.B7A13FC2-ONC1256B5B.00345852@agfa.be>

>> >> Hi:
>> >>
>> >> Dieter and I have put together the promised longer version of the
>> layering
>> >> document.  It is available at
>> >>
>> >>
>>
http://www-db.research.bell-labs.com/user/pfps/semantic-web/layering.html
>> >
>> >"Given that the most attractive layering solution is not possible ..."
>> >
>> >Hmm... at the ftf you didn't conclude that it wasn't possible;
>> >only that it wasn't straightforward. I don't see anything
>> >in this paper that wasn't discussed at the meeting, so
>> >I don't see how you come to the stronger conclusion.
>> >
>> >Why doesn't section 5 discuss the possibilities for resolving
>> >the paradox? An axiom of foundations, intuitionistic logic,
>> >etc. The 4 possibilities discussed at the ftf
>> >meeting seem to have dwindled to 3.
>>
>> also that example at the end of 4.2 contains
>> a cycle with nothing but blank nodes
>> and that is indeed paradoxical, but it
>> can be avoided if we stick with
>> the idea of having blank nodes ``by-value''
>> and not ``by-reference'' (after all, they
>> have no identifier, just maybe a label,
>> but that is *not* an identifier)
>>
>> --
>> Jos
>
>I don't understand how ``by-value'' or ``by-reference'' come into the
>equation here.  Could you expand on this?
>
>peter

sure
having :s :p [ :a :b ] . (which is N3's way
to write :s :p _:o . _:o :a :b)
then there is *no* way to point to that [ :a :b ]
you can however use that [ :a :b ] ``by-value'' i.e.
make a ``copy'' of [ :a :b ] e.g. :x :y [ :a :b ] .
(after all, bnodes are untidy anyway)
so the acyclic and cyclic cases are ruled out that
way and you basically get a ``tree'' where
the leaves are urirefs or literals and the
bnodes are ``branches''
that's the way we do things in Euler, and believe
me, we have no trouble with such cases
(remembering the
:John a [ owl:intersectionOf ( :Student :Person ) ] .
entailing
:John a [ owl:intersectionOf ( :Person :Student ) ] .
using
http://www.agfa.com/w3c/euler/owl-rules.n3)

--
Jos
Received on Saturday, 9 February 2002 05:04:14 GMT

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