Re: compound propositions
Date: Thu, 18 Mar 2010 16:09:26 GMT
David BL wrote:
> So back to your statement, I would say that there is a 1:1
> correspondence from relation (= set of tuples) to a boolean valued
> function that is true for tuples in that relation and false
> otherwise. This boolean valued function can be said to represent a
> predicate under an interpretation but I'm not sure if that's what you
> mean. More specifically, what do you mean by "satisfy" when you say
> relations satisfy predicates?
A relation satisfies one or more predicates when its attribute names match the variable names apparent in the predicates and the attribute types are applicable for whatever manipulations (eg., aggregation) the predicate states.
(I just say 'satisfies' to avoid suggesting that a predicate has a truth value. Don't see anything wrong with talking about correspondence between relations and functions, just seems more to the point to think of another correspondence - tuples that indicate whether propositions are true or false.) Received on Thu Mar 18 2010 - 17:09:26 CET