Composing general logic programs

The program composition approach can be fruitfully applied to combine general logic programs, i.e, logic programs possibly containing negative premises. We show how the introduction of a basic set of (meta-level) composition operations over general programs increases the knowledge representation capabilities of logic programming for non-monotonic reasoning. Examples of modular programming, hierarchical reasoning, constraints, and rules with exceptions will be illustrated. The semantics of programs and program compositions is defined in terms of three-valued logic [15]. The computational interpretation of program compositions is formalised by an equivalence preserving syntactic transformation of arbitrary program compositions into standard general programs.