Integration of functions in the fixpoint semantics of rule-based systems

Abstract

We discuss the integration of functions, types, complex objects and negation in a rule-based system, using the fixpoint semantics. This extension of Datalog is called MilAnt. The rules, the predicates and the functions are typed with complex objects. Functions can be defined to have a result of an arbitrary complex object type. MilAnt consistency is defined as a stronger form of consistency for functions and an algorithm is given to detect the MilAnt consistency in the non-recursive case. To this end, we use a mixture of dependencies that are local to a rule and dependencies that are global for the whole program.