Re: compound propositions
Date: Thu, 18 Mar 2010 15:15:50 -0300
paul c wrote:
>> paul c wrote: >> >>> David BL wrote: >>> ...
>>> A relation satisfies one or more predicates when its attribute names >> >> How do you figure "or more" ? >> ...
> A database with the single attribute 'suppliers' might refer to every
> supplier in the world or only the suppliers in the northwest, whatever
> 'northwest' means.
But a given relation refers to only one or the other.
> Seems an important kind of leverage though I don't know how often it's
> been exploited, eg., the same database could form part of both
That's why we have views, but different views are different relations. Received on Thu Mar 18 2010 - 19:15:50 CET