Re: Coul constraint *enforcement be done at compile time vs runtime ?
Date: Tue, 16 Jun 2009 08:47:58 -0400
"Cimode" <cimode_at_hotmail.com> wrote in message
> As the subject says...
> The traditional direct image system approach consists of having
> relations constraints implemented at the time when the relation is
> updated meaning during UPDATE/DELETE/INSERT operations. As a part of
> a research effort to understand better what may be a relational system
> implementation, I have discovered that it is actually possible to
> perform constraint enforcement at constraint declaration time.
Can you be more specific? Are you saying that /all/ constraints can be enforced at compile time? When a user submits an illogical update, for example, a delete that targets a tuple that is referenced in an inclusion dependency, what do you call the process of determining that it is an illogical update, if not constraint enforcement? Moreover, while domain definitions partition the set of all particulars in the Universe into a set of domains and while state constraints shape the Universe into a set of possible worlds, transition constraints specify which possible worlds are directly accessible from the distinguished actual world, which is represented by the current database value (the redundancy in the terms, 'the' and 'current'.and in the terms 'database' and 'value' being intentional for emphasis). As a consequence, since the enforcement of transition constraints depend on the current database value, how can one determine at constraint declaration time whether a particular update violates a transition constraint?
> Since I have not read anything on the subject, I was wandering and
> hoping for additional references on that specific aspect. I also woul
> dlike to know if previous attempts at building such systems have been
> done in the past.
Received on Tue Jun 16 2009 - 14:47:58 CEST