Current techniques for interpretation of logic programs involve a sequential search of a global tree of procedure invocations. This dissertation introduces the AND/OR Process Model, a method for interpretation by a system of asychronous, independent processes that communicate only by messages. The method makes it possible to exploit two distinct forms of parallelism. OR parallelism is obtained from evaluating nondeterministic choices in parallel. AND parallelism arises in the execution of deterministic fuctions, such as matrix multiplication of divide and conquer algorithms, that are inherently parallel. The two forms of parallelism can be exploited at the same time. This means AND parallelism can be applied to clauses that are composed of several nondeterministic components, and it can recover from incorrect choices in the solution of these components. In addition to defining parallel computations, the model provides a more defined procedural semantics for logic programs; that is, parallel interpreters based on this model are able to generate answers to queries that cause standard interpreters to go into an infinite loop. The interpretation method is intended to form the theoretical framework of a highly parallel non von Neumann computer architecture; the dissertation concludes with a discussion of issues involved in implementing the abstract interpreter on a multiprocessor.

There are two metaphors for describing instrumental computer use: the computer as a tool, and a more comprehensive package metaphor that emphasizes all aspects of computer use (hardware, software, and social interactions with vendors and other actors in the computing world). Whereas the tool view of computing is concerned with the direct costs of hardware and software, the package view helps one estimate all costs -- social and technical -- of instrumental computer use. Data from a case study of two research laboratories that used computers for data collection provides empirical support for a package metaphor.

Logic programs offer many opportunities for parallelism. We present two models of computation which allow parallel processing of Prolog programs. In the goal list model each processor is given a separate approach to the problem. In the AND/OR model each processor is given a separate subcomputation. Each model allows an arbitrary number of processors, and both perform the same sequence of unifications as would the standard depth first interpreter for Prolog if only one processor were available. In each model the parallelism is achieved as a result of the non-determinism in the program.

Logic programs offer many opportunities for parallelism. We present an abstract model that exploits the parallelism due to nondeterministic choices in a logic program. A working interpreter based on this model is described, along with variants of the basic model that are capable of exploiting other sources of parallelism. We conclude with a discussion of our plans for experimenting with the various models, plans which we hope will lead eventually to a multi-processor machine.

The goal of the proposed research is to develop methods for efficient implementation of logic programs. There are two areas we wish to investigate, both of which are continuations of research conducted by members of the UCI dataflow architecture group. One aspect of the proposed research involves development of a non-von Neumann architecture for parallel execution of logic programs; preliminary work in this area is reported by Conery [9]. The second area invovles transformation of high level logic specifications into efficient Prolog and/or procedural language programs, and is based on work by Morris [20].