Corrected definition of locally invertible transformation

"Jan Hidders" <jan.hidders_at_pandora.be> wrote in message news:n9p9b.22067$Wk4.1442847_at_phobos.telenet-ops.be...
> It is a constant function and therefore independent of everything. The way
> you formulated your definition all that I have to show is that if you give
> me a Q and X such that Q(X) is defined then I can construct a
> transformation Q^-1 that maps Q(X) to X. So if you give me X = {
(a=1,b=2),
> (a=1,b=3) } I give you the following transformation:
>
> (SELECT 1 AS a, 2 AS b) UNION (SELECT 1 AS a, 3 AS b)
>
> As you can see there is no reference to an instance, and not even to the
> view. Since I can do this for any X this demonstrates that for any Q and X
> it holds that Q is locally invertable for X.

Given

Q * D = V

Q is called locally invertible if there doesn't exist D' != D, such that

Q * D' = V Received on Mon Sep 15 2003 - 23:18:25 CEST