Re: two nasty schemata, union types and surrogate keys

On Oct 20, 3:18 pm, rp..._at_pcwin518.campus.tue.nl (rpost) wrote:
> Brian wrote:
> >Under the closed world intepretation, every formula that can be
> >represented in a table is assigned a truth value--positive for those
> >that are actually represented in the table and negative for those that
> >aren't, but under the open world interpretation, only those that are
> >actually represented are assigned truth values.  Let's put it another
> >way: either it is supposed to be true or it is known to be true.
> >Under the closed world interpretation, what is represented is supposed
> >to be true, but under the open world interpretation, what is
> >represented is known to be true.  Bottom line: it would be pointless
> >to suppose that what is represented is known to be true.
>
> I can't link this to the notion of closed world assumption
> I'm familiar with.  It doesn't make sense to me.

Maybe you should revisit it, then. For a given predicate and a finite domain there is a finite set of valid propositions, but not every valid proposition is a true proposition. It is only under an interpretation that those propositions are assigned a truth value. Under the closed world interpretation, only and all true propositions are represented as tuples in the relation; under the open world interpretation, only but not necessarily all true propositions are represented as tuples in the relation. In other words, under the closed world interpretation, what is represented is supposed to be true, but under the open world interpretation, what is represented is only what is known to be true.

>
> --
> Reinier
Received on Wed Oct 21 2009 - 04:35:24 CEST