Dynamic composition of parameterised logic modules

We present a logic-based programming language that features meta-level composition operations over programs. Object programs are parameterised named collections of definite clauses which may contain formulae of the form A in Pexp, where A is a standard atomic formula and Pexp is a program expression obtained by applying composition operations over named object programs. The semantics of the language is presented in two different equivalent styles. An operational, top-down semantics is given by means of inference rules, while a denotational, bottom-up semantics is given via an immediate consequence operator associated with program expressions. A meta-programming implementation of the language is also presented by transforming the operational inference rules into meta-level axioms. Several programming examples are discussed to illustrate the expressive power of the language.