Hybrid Rules with Well-Founded Semantics

A general framework is proposed for integration of rules and external first order theories. It is based on the well-founded semantics of normal logic programs and inspired by ideas of Constraint Logic Programming (CLP) and constructive negation for logic programs. Hybrid rules are normal clauses extended with constraints in the bodies; constraints are certain formulae in the language of the external theory. A hybrid program is a pair of a set of hybrid rules and an external theory. Instances of the framework are obtained by specifying the class of external theories, and the class of constraints. An example instance is integration of (non-disjunctive) Datalog with ontologies formalized as description logics. The paper defines a declarative semantics of hybrid programs and a goal-driven formal operational semantics. The latter can be seen as a generalization of SLS-resolution. It provides a basis for hybrid implementations combining Prolog with constraint solvers. Soundness of the operational semantics is proven. Sufficient conditions for decidability of the declarative semantics, and for completeness of the operational semantics are given

Logic programming and rapid prototyping

AbstractLogic programming has great potential for reducing the cost of software development. We argue that, with an appropriate programming methodology, a logic programming system provides a powerful tool for rapid software prototyping. It is sufficiently formal and high-level to allow reasoning about specifications, and it provides an immediate operational validation of the programmer's intuitions.The methodology is introduced by means of an example larger than those usually used to illustrate the advantages of logic programming. We start with an informal specification of a structure-editor, show how it is formalized into a directly executable prototype, and introduce guidelines for validating logic programming code as implemented in Prolog.The developed prototype can be used for a number of applications: syntax-directed editor, semantic network browser, etc. The editor is compact but readable, and is quite efficient

Comparative Metric Semantics for Commit in Or-Parallel Logic Programming

For the control flow kernel of or-parallel Prolog with commit an operational and a denotational model are constructed and related using techniques from metric semantics. By maintaining explicit scope information a compositional handling of the commit for the denotational model is established. By application of an abstraction function, which deletes this extra information the operational semantics is recovered