> 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
