High-level Petri net semantics of concurrent and non-concurrent logic programs

Two new graphical and formal High-Level Petri Net (HLPN) models for expressing and analyzing the declarative and operational semantics of concurrent and non-concurrent logic languages are presented. One is shown to model both families of languages based upon goal-directed operational semantics. The other HLPN is used as a medium for expressing a declarative semantics for a representative concurrent logic language and for studying a process interpretation of the operational semantics of this representative language. Both models are distinct from each other, and from other HLPNs that are widely used, in that their semantics, as expressed through enabling/firing rules and markings, are new.;It is shown how the goal-directed HLPN serves as a both visual and formal model for expressing the SLD-derivations, refutations, and failing computations. By slightly modifying the annotations of the goal-directed HLPN model, several other concepts of logic programming are modeled: built-in atoms; the operational semantics of pure Prolog; SLD-ALG-resolution, a variation of SLD-resolution; and the operational semantics of the concurrent logic language FGHC. It is also shown how the goal-directed HLPNs can be used as a process representation within the framework for a new AND/OR-parallel execution model based upon a shared-memory, multiprocessor architecture.;The other HLPN model focuses on modeling a subset of FGHC as a representative language for concurrent logic languages. This subset language is derived from the denotations that comprise the logical models of a declarative semantics for FGHC. This HLPN model is used to graphically and formally represent an FGHC goal clause and a subset of the denotations associated with the goal clause. Concepts common to the operational semantics of the major concurrent logic languages such as guarded-nondeterminism and synchronization between producer and consumer processes, are modeled. In contrast to the string presentation of the denotations, one has a visual and formal representation of computations that terminate in a successful or failure state, along with ones that lead to deadlock.