Re: [GENERAL] Google Summer of Code: Full Disjunctions

[ana_cata_hylo]

Hi Tzahi

Since you seem to know about full disjunctions, I was wondering if you
could answer this question:

Can full disjunction be implemented as a binary operator?

The algorithms I've seen for computing it seem to require that all
input relations be supplied at once. Even in your message above you
specified your example as FD(A,B,C) rather than say (A fd B) fd C.
So I was wondering if the latter is possible?

The reason I ask is that I'm currently trying to solve a problem that
could in principle be solved using FD but it would fit into my current
framework much better if it were a binary operator like the other
joins.

Thanks in advance.
Lee


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Re: [GENERAL] Google Summer of Code: Full Disjunctions

[ana_cata_hylo]

> First, i have no knowledge of anyone that have implemented full 
> disjunctions(ever) aside
> from the theoretical works of my colleagues.
> With the exception of a corner case of it, that I believe was a simulation in 
> 96.
> (A. Rajaman and J.D. Ullman Integrating information by outerjoins and 
> full-disjunctions).
> I'd love to hear about any implementation out there (aside from my colleagues 
> work, which
> is mine also: cohen,sagiv, kimelfeld,kanza)

I didn't mean to imply there was. It was the Rajaraman & Ullman paper
that got me interested in FD's and then I've looked at the "Computing
Full Disjunctions" paper by Kanza & Sagiv which gives a general
solution.
Obviously from the second paper it's clear that implementing full
disjunction (efficiently) is a non-trivial exercise.

> It can never be a binary operation since at the heart of the matter is that 
> you need to take
> each subset of the relations and join them. i.e.:
...
> Usually binary operations allow for a bottom up computation approach, but FD 
> is a TOP down approach
> (Galindo-Legaria, C. outerjoins as disjunctions).

Right, thanks for clarifying.

>From a data analysis perspective I would like to be able to look at
various subsets, eg. FD(A,B,C), FD(B,C,D), FD(A,B,C,D) etc and so this
just means that each subset has too be computed independantly. I can
live with that but wasn't sure if I had missed something.

In any case, the difficulty of implementing FD precludes me from
experimenting with it just yet.

Regards
Lee


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