Re: What is an automorphism of a database instance?
From: Kira Yamato <kirakun_at_earthlink.net>
Date: Wed, 9 Jan 2008 19:02:47 -0500
Message-ID: <2008010919024775249-kirakun@earthlinknet>
>
> 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)
Date: Wed, 9 Jan 2008 19:02:47 -0500
Message-ID: <2008010919024775249-kirakun@earthlinknet>
On 2008-01-09 18:53:17 -0500, Tegiri Nenashi <TegiriNenashi_at_gmail.com> said:
> 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)
Of course, it's obvious from the definition!
Thanks.
>
> AFAIR in lattice theory an order isomorphism is the same as
> isomorphism defined in terms of operations /\ and \/.
-- -kiraReceived on Wed Jan 09 2008 - 18:02:47 CST