The Use of Renaming in Composing General Programs

Most modern computing systems consist of large numbers of software components that interact with each other. Correspondingly, the capability of re-using and composing existing software components is of primary importance in this scenario. In this paper we analyse the role of renaming as a key ingredient of component-based programming. More precisely, a meta-level renaming operation is introduced in the context of a logic-based program composition setting which features a number of other composition operations over general logic programs, that is, logic programs possibly containing negative premises. Several examples are presented to illustrate the increased knowledge representation capabilities of logic programming for non-monotonic reasoning. The semantics of programs and program compositions is defined in terms of three-valued logic by extending the three-valued semantics for logic programs proposed by Fitting [10]. A computational interpretation of program compositions is formalised by means of an equivalence preserving transformation of arbitrary program compositions into standard general programs.