We propose a method of parallelizing bottom-up-evaluation of logic programs. The method does not introduce interprocess communication, or synchronization overhead. We demonstrate that it can be applied when evaluating several classes of logic programs, e.g., the class of linear single rule programs. This extends the work reported in [WS] by significantly expanding the classes of logic programs that can be evaluated in parallel. We also prove that there are classes of programs to which the parallelization method cannot be applied.

Sharing the Load of Logic-Program Evaluation.

In this paper we will discuss several methods for recursive query processing using a recursive control structure. We will describe the QSQR method, introduced in [Vie861 and show that it fails to produce all answers in certain cases. After analyzing the causes of this failure we propose an improved algorithm the RQA/FQI Strategy which is complete over the domain of function-free Horn clauses. The new method uses a two step approach recursive expansion + an efficient variant of LFP iteration to evaluate recursive queries. A short comparison of these methods shows the efficiency of RQA/FQI.

/pdf/recursive-strategies-for-answering-recursive-queries-the-rqa-3wkh67ldyx.pdf

Recursive Strategies for Answering Recursive Queries - The RQA/FQI Strategy

In this paper we consider selections of the form “column = constant” on relations defined by linear recursive, two rule datalog programs. In general, counting methods perform well on such queries. However, counting methods fail in the presence of cycles in the database. We present an algorithm in the spirit of counting methods that correctly deals with cyclic data and has the same asymptotic running time as counting methods. The algorithm, which is based on reducing a query on a database to a question about intersections of semi-linear sets, works by using efficient methods to construct the appropriate semi-linear sets from the database and query constant.

Counting methods for cyclic relations

Sharing the load of logic-program evaluation

If $G$ is a directed graph with labeled edges and $L$ is a fixed regular language, the {\em regular path problem}, given two nodes, $u$ and $v$, in $G$, is to find a path between $u$ and $v$ such that the labels on the arcs along that path form a string which is a member of $L$. We consider a dynamic version of this problem, adding arcs to and performing regular path queries on $G$ over $L$, and present a data structure that solves both problems in average time per operation linear in the number of nodes of the graph for any fixed regular language.

A data structure for arc insertion and regular path finding

Worst-case complexity analysis of methods for logic query implementation

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Worst-case complexity analysis of methods for logic query implementation