Re: n-ary operations

On Thu, 11 Dec 2014 11:15:12 -0500, ruben safir <ruben_at_mrbrklyn.com> wrote:

>I have this quote fro a textbook
>
>6.2.2 The CARTESIAN PRODUCT (CROSS PRODUCT)
>Operation
>Next, we discuss the CARTESIAN PRODUCT operation—also known as CROSS
>PRODUCT or CROSS JOIN—which is denoted by ×. This is also a binary set
>opera-
>tion, but the relations on which it is applied do not have to be union
>compatible. In
>its binary form, this set operation produces a new element by combining
>every
>member (tuple) from one relation (set) with every member (tuple) from
>the other
>relation (set). In general, the result of R(A1, A2, ..., An) × S(B1, B2,
>..., Bm) is a rela-

     R is an n-ary operation. It has n operands.

     S is an m-ary operation. It has m operands.

>tion Q with degree n + m attributes Q(A1, A2, ..., An, B1, B2, ..., Bm),
>in that order.

     Q is an (n+m)-ary operation. It has n+m operands.

>The resulting relation Q has one tuple for each combination of
>tuples—one from R
>and one from S. Hence, if R has nR tuples (denoted as |R| = nR), and S
>has nS tuples,
>then R × S will have nR * nS tuples.
>The n-ary CARTESIAN PRODUCT operation is an extension of the above concept,
>which produces new tuples by concatenating all possible combinations of
>tuples
>from n underlying relations.

>What is an n-ary operation? I see this repeadely but I am not
>understanding its meaning.

     The operation takes n operands.

Sincerely,

Gene Wirchenko Received on Thu Dec 11 2014 - 18:15:24 CET