W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > July 2001

Re: A use case for anon nodes - action from telecon

From: <jos.deroo.jd@belgium.agfa.com>
Date: Wed, 25 Jul 2001 01:41:10 +0100
To: phayes@ai.uwf.edu
Cc: Graham.Klyne@Baltimore.com, w3c-rdfcore-wg@w3.org
Message-Id: <OF11CB5969.637BAFBE-ON41256A93.0081657D@bayer-ag.com>

[...]
> Right, though that "(in some sense)" deserves to be made more
> explicit, which I will try to do before the f2f meeting. I mean, it
> is an existential, strictly speaking, but queries are functionally
> similar to *negated* assertions, so the machinery you need to handle
> an existential in a query is the same as what you need to handle a
> universal in an assertion. This is one of those things that just kind
> of gets to be part of the atmosphere to anyone working in logic. In
> most inference engines you can't tell asserted existentials from
> queried universals, and vice versa.

I'm really glad you express it so clear
and I think you couldn't be more right :-)
This is indeed related with Modus Tollens (MT)
  given P->Q and ~Q we can deduce ~P
  (Q like the Query and P like the Premiss
  an P becoming now a new given sub-query etc.)
and ~forall is like forsome so indeed
  you can't tell asserted existentials from
  queried universals, and vice versa.
and I still think this is kind of what also
happens in the 'mini' world of anonymous node
resolution (which is kind of generalized MT)

??? could it be that [ :p :o] (as one token)
is an existental but that we *could* assert
forall _:s such that _:s :p :o. ???
(we actually do use the former and then
query with some kind of univeral/template
(which can contain the 'normal' existentials))

--
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Tuesday, 24 July 2001 19:42:15 EDT

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