Re: database design method
From: Alfredo Novoa <alfredo_at_nospam_ncs.es>
Date: Thu, 07 Nov 2002 21:50:30 GMT
Message-ID: <3dcad503.381118_at_newscache4.freenet.de>
Date: Thu, 07 Nov 2002 21:50:30 GMT
Message-ID: <3dcad503.381118_at_newscache4.freenet.de>
On 7 Nov 2002 10:48:42 +0100, hidders_at_REMOVE.THIS.uia.ua.ac.be (Jan
Hidders) wrote:
>Is this set of languages really a set in the sense that there is a proper
>definition of it in set theory?
No.
> Or is there just a set of properties that
>should hold for the language (in which case it might be a class rather then
>a set).
It is a set of prescriptions, proscriptions and recomendations for constructing relational languages.
>Anyway, is there a proof somewhere
>that Tutorial-D is computationally complete?
Yes, because it also has imperative extensions.
>Ok. Can I express that relation R2 is the transitive closure of relation R1?
Yes:
R2 := TClose R1; Received on Thu Nov 07 2002 - 22:50:30 CET