Re: Idempotence and "Replication Insensitivity" are equivalent ?

Chris Smith wrote:
> <pamelafluente_at_libero.it> wrote:
> > this is an exaggeration. Everyone knows that the variance is simply
> > the difference between the second moment and the square of the
> > first moment. So you just need to accumulate values and their squares.
>
> Ah. In that case, variance (and standard deviation) are efficient
> aggregate functions.
>

Boy you are really hung up on nomenclature.

First of all you don't want an aggregate function to be any function on M(A) (which is how Oracle apparently defines them). Okay call such functions turquoise functions. You define, without motivation, a subclass of turquoise functions which you call the aggregate functions. Are these supposed to be the efficiently computable turqoise functions? If so what is an efficient aggregate function?

In any case there are interesting turquoise functions that are replication insensitive, but for which there is no justification for calling them idempotent. So although the two concepts are related they are not the same.

                           -William Hughes