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Re: How to derive a consistent set of FOL constraints

From: Dmitry Tsarkov <dmitry.tsarkov@gmail.com>
Date: Mon, 5 Mar 2007 23:42:11 +0000
Message-ID: <7b84f3a00703051542qf183752n5e4dd36fbc6b4b34@mail.gmail.com>
To: "John F. Sowa" <sowa@bestweb.net>
Cc: "Ontology Summit 2007 Forum" <ontology-summit@ontolog.cim3.net>, lobrst@mitre.org, ezolin@cs.man.ac.uk, public-owl-dev@w3.org, matthew.williams@cancer.org.uk, semantic-web@w3.org
On 3/5/07, John F. Sowa <sowa@bestweb.net> wrote:
> Yet every SQL database
> permits arbitrary first-order constraints.
> Q: How is possible to prove that the constraints are consistent?
> A: Trivially.
> The point is that no database designer *ever* begins with
> an arbitrary set of constraints.  They *always* begin with
> some actual data -- a sample DB that shows what kind of data
> they expect to work with.

Simple idea that comes to my mind immediately: the DB is a *closed  world*,
i.e. if something is not there, this does not hold.

It is different for the DL, which is an *open world*. That means if some
fact is not known to be true, it can be either true or false (in a
particular world). This means, that the search space is exponentially larger
in case of description logic comparing to DBs.

> John

Received on Tuesday, 6 March 2007 20:38:53 UTC

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