Graph-Based Processing of Logic Programs

A lot of practical recursive logic queries to a deductive database are expressed by linear recursive Datalog programs with exactly one recursive rule, so-called linear sirups. We give a characterization of k-sided linear Datalog sirups -- the concept was introduced by Naughton in [22] -- based on a graph model and present a normal form to which every linear Datalog sirup can be transformed. Normalized linear Datalog sirups can be decomposed by a counting technique into k lower-dimensional linear sirups which can be evaluated in parallel by very efficient query evaluation algorithms. For certain sets of linear sirups defining the same intensional predicate we can also derive a decomposition approach from the graph model. Another technique based on the prefixes of compiled expansions transforms a set of chain rules with binary predicate symbols, a so-called CFG program, into a transition graph. Common subexpressions between different compiled formulas can be detected by the graph mini..