Re: Proposal: 6NF
Date: Thu, 19 Oct 2006 17:18:07 -0700
Message-ID: <a85gj2tqodnhjnu1huvk7k2m71sdrcl93u_at_4ax.com>
"vc" <boston103_at_hotmail.com> wrote:
>JOG wrote:
[snip]
>> As far as I understood from my school years, an operation just mapped
>> one set of values to another. I remain unconvinced of the need for an
>> operation upon a set to map to itself.
>
>f:SxS -> S is not "a set to map to itself". We are talking here about
The page you suggested sure seems to say that though!
>very very basic stuff that's known if not from the primary school then
>at least from the secondary school agebra (or at least should be).
>
>>Where is such a definition? As I
>> said, I am open to convincing, but I was not aware of such a
>> pre-requisite for closure?
>
>If books are not read any more nowadays, then this might help:
>
>http://mathworld.wolfram.com/BinaryOperation.html
Look at clause 2.
"Binary Operation
A binary operation f(x,y) is an operation that applies to two quantities or expressions x and y.
A binary operation on a nonempty set A is a map f:AxA->A such that
- f is defined for every pair of elements in A, and
- f uniquely associates each pair of elements in A to some element of A.
Examples of binary operation on A from AxA to A include addition (+), subtraction (-), multiplication (x) and division (÷)."
Sincerely,
Gene Wirchenko
Computerese Irregular Verb Conjugation:
I have preferences. You have biases. He/She has prejudices.Received on Fri Oct 20 2006 - 02:18:07 CEST