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Re: worries about useMentionOp and how queries relate to rules and proofs

From: <jos.deroo@agfa.com>
Date: Fri, 4 Feb 2005 02:35:47 +0100
To: connolly@w3.org
Cc: "Eric Prud'hommeaux" <eric@w3.org>, Pat Hayes <phayes@ihmc.us>, www-archive@w3.org
Message-ID: <OF0E4763A6.FAE99FCA-ONC1256F9E.0006ED9A-C1256F9E.0008C4C4@agfa.com>

Dan, it worries me very much and I'm pretty convinced
that such operators are not needed at all to do SW which
is about marking data so that computers are also able to
process it and test relationships between different datasets

Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/

Dan Connolly <connolly@w3.org>
04/02/2005 01:39

        To:     Pat Hayes <phayes@ihmc.us>
        cc:     www-archive@w3.org, "Eric Prud'hommeaux" <eric@w3.org>, Jos 
        Subject:        worries about useMentionOp and how queries relate to rules and  proofs


I can't quite put my finger on it, but I'm afraid there are
some serious architectural use/mention issues with operators like
BOUND, URI-equal, isURI, and isBlank

As I see the architecture, a query plays the role of
a conjecture to be proved. A query solution is a sketch
of a proof.

If I write

 SELECT ?who
 WHERE ?who foaf:name "Dan Connolly"

it's akin to asking a theorem prover to prove:

  exists (x) such that foaf:name(x, "Dan Connolly")

The solution "?who binds to <danshomePage#topic>"
is a sketch of a proof (I think the literature
uses the term "witness" for this sort of thing).

Now I can't imagine how to turn

 SELECT ?who
 WHERE ?who foaf:homePage ?x
   AND isURI(?x)

into a conjecture to be proved by a theorem prover.
isURI() is not a function of objects in the
domain of discourse, but an operator that distinguishes
one sort of term from another. We might have

                 <dansHomePage#topic> owl:sameAs _:somebody .
and by definition
but not

This sets off flags in my mind, but I can't state,
in black-and-white, testable ways that matter to
applications and coders, why it matters.

Does it worry you?

p.s. formally this is a WG issue
In Helsinki, we has some relevant discussion and made
a nearby decision, but it wasn't explicitly a decision
to close this issue.

  RESOLVED: BOUND keyword and no UNSAID to address common
  UNSAID issues. KendallC abstaining

I'm trying to figure out whether to open substantive discussion
of this useMentionOp issue or just say "oh... yeah, we meant to close
that one too, didn't we?"

Dan Connolly, W3C http://www.w3.org/People/Connolly/
D3C2 887B 0F92 6005 C541  0875 0F91 96DE 6E52 C29E
Received on Friday, 4 February 2005 01:36:28 UTC

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