Showing papers on "Join (sigma algebra) published in 1985"

Some experimental results on distributed join algorithms in a local network

Abstract: This paper presents some experimental results on the performance of distributed join algorithms in a local network. Eight different join methods have been implemented in an experimental distributed system, the Crystal multicomputer, and tested for join queries with a variety of relation sizes, join selectivities, and join column value distributions. The results obtained indicate that pipelined join methods outperform sequential methods over a wide range of join queries. It was also found that the communications costs in a local network environment are not a dominant factor with respect to performance, and that shipping a whole relation from one site to another is not an unreasonahle decison as long as it is done in the framework of pipelined algorithms. Two pipelined variants of a centralized nested loops join algorithm (with an index) were found to perform well for many of the queries tested.

The Birkhoff Variety Theorem for continuous algebras

Abstract: Varieties of continuous algebras, i.e., classes presented by (in)equalities for terms, are characterized as precisely the HSP classes. Terms here are the usual algebraic terms enriched by iterated join symbols. A discussion of varieties which require only finitely many variables, or only the usual terms, is also presented.

The lower central series in some groups with the subnormal join property

Abstract: The following question is considered: What groups G are such that, given any subnormal subgroups H and K of G, with join J, and given any positive integers