Re: RM and definition of relations/tuples

Martin Zapf wrote:
> 1. defintion:
>
> A relation r for schema R is a mathematical relation (cartesian
> product) over the
> domains from the attributes of R.
> So r:=dom(A_1)xdom(A_2)x...xdom(A_n)
> A tuple is an element of r.
>

out of curiosity does this first definition originate from? Definition 2 certainly seems on the money to me, but in the first definition I see no mapping from value to attribute - this would seem essential to me given such a mathematical formalisation (attributes can't be automagically known externally to a system which presupposes that they may vary?).

All best, J. Received on Fri Nov 25 2005 - 11:29:09 CET