Re: Is a function a relation?

From: David BL <>
Date: Thu, 25 Jun 2009 21:54:31 -0700 (PDT)
Message-ID: <>

On Jun 25, 5:32 pm, "Brian Selzer" <> wrote:


> But a database relation is not the same thing as a mathematical relation.
> The difference may not be immediately obvious--and I'm not referring to the
> fact that components of tuples in a database relation are named whereas
> components of tuples in a mathematical relation are indexed. The difference
> is in how the relations are arrived at, and the extent to which they endure.
> In the case of a database relation, the predicate is extended and each
> atomic formula is judged to be either true or false at the instant of
> interpretation, but in the case of a mathematical relation, the predicate is
> extended and there is no need to judge whether each atomic formula is true
> or false because owing to the fact that whenever there is a particular
> abstract object, it is necessary that there is that particular abstract
> object, each atomic formula in the extension of a mathematical relation is
> true necessarily. So for mathematical relations, one can safely dispense
> with judging the truths of the atomic formulae represented by tuples. Also,
> the assignment of meaning to terms in the atomic formulae in the extension
> of mathematical relations can be deferred because abstract objects neither
> come into existence, change in appearance nor cease to exist. It is
> tempting, therefore, to treat database relations as mathematical relations,
> and one safely can for activities or specifications that involve just one
> instance at a time, such as queries or the specification of referential
> constraints, but the danger in expanding the scope of activities or
> specifications so that they involve more than one instance at a time, as is
> the case for updates, is that there would be more than one assignment of
> meaning and more than one judgement of truth for the same activity.

I don't know what that means, so I'll ask some questions to try to establish a common point of reference!

Received on Fri Jun 26 2009 - 06:54:31 CEST

Original text of this message