Akira Aiba

CAL: A theoretical background of constraint logic programming and its applications

Constraint logic programming (CLP) is an extension of logic programming by introducing the facility of writing and solving constraints in a certain domain. CAL (Contrainte avec Logique) is a CLP language in which (possibly non-linear) polynomial equations can be written as constraints, while almost all the other CLP languages proposed so far have concentrated only on linear equations and inequations. This paper describes a general semantics of CLP including CAL, and shows the validity of CAL in this framework.

HETEROGENEOUS DISTRIBUTED COOPERATIVE PROBLEM SOLVING SYSTEM HELIOS AND ITS COOPERATION MECHANISMS

For advanced and complicated knowledge processing, we need to integrate various kinds of problem-solvers such as constraint solvers, databases, and application programs. A heterogeneous distributed cooperative problem solving system HELIOS achieves this integration by introducing capsule and environment modules. To integrate heterogeneous problem-solvers that may be implemented in different languages and may have different knowledge representations, those heterogeneity should be absorbed. Capsules and environments are introduced into HELIOS for this purpose. A capsule surrounds each problem-solver and translates the contents of communication to and from the internal representation and a common representation. We call an encapsulated problem-solver an agent. An environment is a module which provides a field giving common representation, and agents communicate and cooperate with each other in each environment. Since an encapsulated environment with its agents can be considered as an agent, agent-environment structures can be nested in HELIOS. For negotiation between agents, negotiation protocol can be defined in each environment. A negotiation strategy that suits the given negotiation protocol can be defined in each capsule of an agent. In this framework, we define a transaction-based negotiation protocol. To check the validity of HELIOS design and its implementation model on computers connected by network, we implemented an experimental version of HELIOS on UNIX workstations.

The parallel logic programming system in the FGCS project and its future directions

Abstract In the fifth generation computer systems (FGCS) project, a parallel logic programming language, KL1, was adopted as the projects kernel language. It was not only used to determine architectures of highly parallel machines called parallel inference machines (PIMs) consisting of about 1000 element processors but also used as a system description language to develop basic software such as a parallel operating system (PIMOS), and symbolic processing and knowledge processing application systems such as knowledge description languages, a parallel theorem prover, and a protein sequence analysis program. It achieved great success in exploiting of parallelism involved in several important application systems. The prototype of the FGCS attained a linear speed-up that was proportional to the number of processing elements (PEs) for the application systems we had targeted. The MGTP parallel theorem prover was one of such application systems, and can prove theorems based on full first-order logic. Thus, it indicates the possibility of designing a new practical knowledge representation language whose expressive power will be much greater than that of conventional ones. In the FGCS follow-on project, KL1 and its programming system were ported to Unix-based stock parallel machines. This new system called KLIC is expected to greatly extend the use of highly parallel systems.