Re: SUPPORT FOR DECLARATIVE TRANSITION CONSTRAINTS

On Sep 27, 5:24 am, Erwin <e.sm..._at_myonline.be> wrote:
> > 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."

Definite descriptions are terms. They're complex terms, but they're terms nonetheless.

"the employee named paul c" differs from "there is one and only one employee named paul c" in that under an interpretation, "the employee named paul c" maps to an element in the domain of discourse whereas "there is one and only one employee named paul c" maps to an element in the domain of truth values.

'The x such that Qx' expresses that there is exactly one x that satisfies Q, but it is also a term: it is exactly that x that satisfies Q. Of course if there is no x such that Q, then the definite description fails to denote, and as a consequence any atomic formula that references the description is, by definition, false, along with the expression, 'there is exactly one x that satisfies Q.'

R-tuples represent propositions that are composed of an n-place predicate symbol along with an ordered n-tuple of terms. Relations in the database represent collections of propositions with the same predicate symbol that are supposed to be true, but only during the interval in time that began at the instant of the last transition and hasn't yet ended.

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

Sorry, can't do it: don't have it.

> > 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.

This is just plain pathetic. How would the system answer the query, "Is there an employee named paul c?" I don't think 'maybe' is an acceptable answer.

>
> > 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.

How can you possibly make such a bald assumption?

<snip> Received on Mon Sep 27 2010 - 15:14:15 CEST