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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 
De_Roo/AMDUS/MOR/Agfa-NV/BE/BAYER@AGFA
        Subject:        worries about useMentionOp and how queries relate to rules and  proofs


Pat,

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
  http://www.w3.org/2001/sw/DataAccess/issues#useMentionOp

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
                 isURI(<dansHomePage#topic>)
but not
                 isURI(_:somebody)

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
  http://www.w3.org/2001/sw/DataAccess/issues#useMentionOp
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
  http://www.w3.org/2001/sw/DataAccess/ftf4.html#item04

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 GMT

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