Parallelizing datalog: function symbols make a difference

A Datalog program consists of function-free Horn clause rules. There are, however, some situations described more easily and more naturally by the use of general terms as arguments. A term is built up from variables, constants, and function symbols. A set of rules where the rules may contain function symbols is called a Datalog^Fun program. The paper discusses parallel processing of decomposable Datalog ^Fun programs to overcome the performance problem. A decomposable program can be evaluated in parallel such that neither a communication nor a synchronization of the processors has to be established. The author and G. Lausen (1991) proposed the concept of generalized pivoting as a sufficient condition for decomposability of arbitrary but function-free Datalog programs. The current paper extends the concept of generalized pivoting to programs which may contain function symbols