Re: What is an automorphism of a database instance?

On Jan 9, 3:29 pm, Kira Yamato <kira..._at_earthlink.net> wrote:
> BTW, do we need to impose partial ordering preserved too? Partial
> ordering defined as
> A <= B
> if and only if
> A = A /\ B.

A = A /\ B
imply
f(A) = f(A /\ B)
which implies
f(A) = f(A) /\ f(B)
which in turn imply
f(A) <= f(B)

AFAIR in lattice theory an order isomorphism is the same as isomorphism defined in terms of operations /\ and \/. Received on Thu Jan 10 2008 - 00:53:17 CET