Re: The Practical Benefits of the Relational Model
Date: 8 Oct 2002 09:25:13 -0700
Message-ID: <72f08f6c.0210080825.240fd3ff_at_posting.google.com>
Costin Cozianu <c_cozianu_at_hotmail.com> wrote in message news:<anssud$haqdr$1_at_ID-152540.news.dfncis.de>...
> Try to look at it from a semantic perspective.
Thanx for the tip.
[snip]
> What happens by Date's updatability rules in the general case (c doesn't
> break any integrity constraints on A and B). The tuple c gets inserted
> both into A and B, therefore the DBMS takes my words and transforms them
> into "I know that PA(c) AND PB(c)".
The OR in question is inclusive, it very well could be the case that PA(c) AND PB(c) is true. Moreover, the updatability mechanism is capable of determining when this is the case, and when it is not.
[snip]
> Have you considered this alternative ?
We allow the user to write relational operators, and define the update semantics for them.
Regards
Bryn Rhodes
Alphora
Received on Tue Oct 08 2002 - 18:25:13 CEST