A Similarity-Based WAM for Bousi~ Prolog

Proc. of IX Jornadas sobre …, 2009

dectau.uclm.es

Bousi∼Prolog is an extension of the standard Prolog language aiming at to make more flexible the query answering process and to deal with vagueness applying declarative techniques. In this paper we precise a model-theoretic semantics for a pure subset of this language, we recall both the WSLD-resolution principle and a similarity-based unification algorithm which is the basis of its operational mechanism and then we prove the soundness of WSLD-resolution.

Electronic Notes in …, 2009

Bousi~Prolog is an extension of the standard Prolog language. Its operational semantics is an adaptation of the SLD resolution principle where classical unification has been replaced by a fuzzy unification algorithm based on fuzzy relations defined on a syntactic domain. In this paper we describe how BousiProlog may contribute to resolve several problems extracted from different application areas, where it is mandatory to deal with vagueness and uncertain knowledge, such as: flexible deductive databases, fuzzy control, fuzzy experts systems, data retrieval or approximate reasoning. Hence, through several (small but meaningful) examples we show the great potential of this programming language.

In Proc. of the 10th IASTED …, 2006

The implementation of Prolog systems has a long history, starting from the first interpreter written in 1972, to the first Prolog compiler simplifying basic operations like unification and backtracking with the aim of optimizing performances, and to the Warren Abstract Machine, later becoming a de facto standard model. The tuProlog engine differs from those systems in that maximum efficiency is not amongst its primary concerns. Instead, it aims at becoming the enabling technology for building complex systems like dynamic Internet infrastructures based on intelligent components, a domain where logic languages could effectively face, in principle, the key issues of intelligence and interaction. To accomplish this task, a logic engine must meet engineering properties such as deployability, configurability and scalability; to be usable as a development tool, it also must sustain a certain degree of traceability, by allowing the inspection of its internal processes at runtime, thus easying the typical pain of debugging activities. The design and implementation of such a system must follow sound principles: object-oriented code structuring, reuse of established community knowledge under the form of patterns, loose coupling of composing elements, modularity and a clear and clean separation of concerns. In this paper, we present the architecture of tuProlog, based upon a set of managers handling control of sensible parts of the system and operating around a minimal core shaped as a Finite State Machine; then, the representation of Prolog data and the unification algorithm's implementation are discussed; finally, the resolution part of the engine is illustrated.

actapress.com

Advances in Computational …, 2011

Bousi∼Prolog is an extension of the standard Prolog language aiming at to make more flexible the query answering process and to deal with vagueness applying declarative techniques. In this paper we precise a model-theoretic semantics for a pure subset of this language. Next, for the first time, we define a notion of correct answer which provides a declarative description of the output of a program and a goal in the context of a similarity relation. Afterwards, we recall both the WSLDresolution principle and a similarity-based unification algorithm which is the basis of its operational mechanism and then we prove the soundness of WSLD-resolution.

International Conference on Logic Programming, 2018

We take a fresh, "clean-room" look at implementing Prolog by deriving its translation to an executable representation and its execution algorithm from a simple Horn Clause meta-interpreter. The resulting design has some interesting properties. The heap representation of terms and the abstract machine instruction encodings are the same. No dedicated code area is used as the code is placed directly on the heap. Unification and indexing operations are orthogonal. Filtering of matching clauses happens without building new structures on the heap. Variables in function and predicate symbol positions are handled with no performance penalty. A simple Englishlike syntax is used as an intermediate representation for clauses and goals and the same simple syntax can be used by programmers directly as an alternative to classic Prolog syntax. Solutions of (multiple) logic engines are exposed as answer streams that can be combined through typical functional programming patterns, with flexibility to stop, resume, encapsulate and interleave executions. Performance of a basic interpreter implementing our design is within a factor of 2 of a highly optimized compiled WAM-based system using the same host language. To help placing our design on the fairly rich map of Prolog systems, we discuss similarities to existing Prolog abstract machines, with emphasis on separating necessary commonalities from arbitrary implementation choices.

Parallel Computing, 1992

This paper presents two algorithms as extensions to the basic Resolution Principle of logic programs which exploit parallelism retaining the full semantics of Prolog. The first algorithm, called SPU, allows parallel execution of unifications belonging to deterministic paths of the proof tree, giving in effect AND-parallel execution. The second algorithm, called MPU, retains the benefits of SPU while exploiting OR-parallelism. We also present simulation results which are indicative of the performance of the proposed algorithms and finally we discuss implementation issues which give rise to the development of a parallel machine.