From: Erwin <>
Date: Mon, 27 Sep 2010 02:24:09 -0700 (PDT)
Message-ID: <>

> You obviously missed the introductory "Assuming that no other
> proposition references an employee named paul c or a position named
> toilet scrubber."  There are more than one reason for the proposition
> to be judged false. ... Given only the negative
> information,
> It is not the case that the employee named paul c fills the position
> named toilet scrubber.

Formulation is flawed, and I suppose deliberately so, with the intent of misleading the reader into your stupid traps.

Correct formulation is, of course, "It is not the case that there exists an employee named paul c who fills the position named toilet scrubber."

Read the piece of text about negation in "Logic and Databases".

> it cannot be proven that there is in fact an employee named paul c, or
> that there is in fact a position named toilet scrubber.

Under your own assumption that no other relvars reference "employees named paul c", or "positions named toilet scrubber", it can reasonably be expected that no one will ever have a need for any such proof, and you should simply abstain from dragging such considerations in your own example.

> is the only place where "the employee named paul c" is referenced in
> the database, then under the domain closure assumption,  DELETEing
> that tuple not only denies the propsition that it represents, but also
> denies the proposition "there is an employee named paul c."

No. The latter proposition is irrelevant to the business at hand. And thus its trueness or falsehood is too. And you should abstain from dragging such propositions into the discussion, because it was you defined such propositions as irrelevant when you said that no other relvars say anything about employee names. Received on Mon Sep 27 2010 - 11:24:09 CEST

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