Abstract not found

Abstract not found

The design of linear logic programming languages and theorem provers opens a number of new implementation challenges not present in more traditional logic languages such as Horn clauses (Prolog) and hereditary Harrop formulas (λProlog and Elf). Among these, the problem of efficiently managing the linear context when solving a goal is of crucial importance for the use of these systems in non-trivial applications. This paper studies this problem in the case of Lolli [HM94], though its results have application to other systems. We first give a prooftheoretic presentation of the operational semantics of this language as a resolution calculus. We then present a series of resource management systems designed to eliminate the nondeterminism in the distribution of linear formulas that undermines the efficiency of a direct implementation of this system. 1

Functional and logic programming are the most important declarative programming paradigms, and interest in combining them has grown over the last decade. However, integrated functional logic languages are currently not widely used. This is due to the fact that the operational principles are not well understood and many different evaluation strategies have been proposed which resulted in many different functional logic languages. To overcome this situation, we propose the functional logic language Curry which can deal as a standard language in this area. It includes important ideas of existing functional logic languages and recent developments, and combines the most important features of functional and logic languages. Thus, Curry can be the basis to combine the currently separated research efforts of the functional and logic programming communities and to boost declarative programming in general. Moreover, since functions provide for more efficient evaluation strategies and ...

Logic languages can deal with non-deterministic computations via built-in search facilities. However, standard search methods like global backtracking are often not sufficient and a source of many programming errors. Therefore, we propose the addition of a single primitive to logic-oriented languages to control non-deterministic computation steps. Based on this primitive, a number of different search strategies can be easily implemented. These search operators can be applied if the standard search facilities are not successful or to encapsulate search. The latter is important if logic programs interact with the (non-backtrackable) outside world. We define the search control primitive based on an abstract notion of computation steps so that it can be integrated into various logic-oriented languages, but to provide concrete examples we also present the integration of such a control primitive into the multi-paradigm declarative language Curry. The lazy evaluation strategy of Curr...

Introducing types into a logic programming language leads to the need for typed unification within the computation model. In the presence of polymorphism and higher-order features, this aspect forces analysis of types at run-time. We propose extensions to the Warren Abstract Machine (WAM) that permit such analysis to be done with reasonable efficiency. Much information about the structures of types is present at compile-time, and we show that this information can be used to considerably reduce the work during execution. We illustrate our ideas in the context of a typed version of Prolog. We describe a modified representation for terms, new instructions and additional data areas that in conjunction with existing WAM structures suffice to implement this language. The nature of compiled code is illustrated through examples, and the kind of run-time overheads that are incurred for processing types is analyzed, especially in those cases where others have shown that type checking can be eliminated during execution. The ideas

This paper examines implementation problems that arise from providing for aspects of higher-order programming within and enhancing the meta-language abilities of logic programming. One issue of concern is a representation for the simply-typed lambda terms that replace the usual first-order terms as data structures; this representation must support an efficient realization of ...-conversion operations on these terms. Another issue is the handling of higher-order unification that becomes an integral part of the computational model. An implementation must cater to the branching nature of this operation and also provide a means for temporarily suspending the solution of a unification problem. A final issue concerns the treatment of goals whose structure is not statically apparent. These problems are discussed in detail and solutions to them are described. A representation for lambda terms is presented that uses the de Bruijn "nameless" notation and also permits reduction substitutions to be performed lazily. This notation obviates ...-conversion and also supports an efficient implementation of ...-reduction. Branching in unification is implemented by using a depth-first search strategy with backtracking. A structure that is called a branch point record and is akin to the choice point record of the Warren Abstract Machine (WAM) is described for remembering alternatives in unification. An explicit representation for unification problems is presented that permits sharing and also supports the rapid reinstatement of earlier versions of the problem. The implementation of unification is tuned to yield an efficient solution to first-order like problems, in fact through the use of compiled code as in the WAM. A compilation method is also discussed for goals whose structure changes during execution. Th...

. In this paper we present a method for translating Horn clauses extended with modalities and embedded implication (which provide reasoning capabilities in a multiagent situation and hypothetical reasoning) into Horn clauses, therefore suitable for SLD resolution. The translation takes two steps: the first one eliminates embedded implications by introducing new modalities; the second eliminates modalities by adding an argument which represents the worlds of the Kripke semantics to all predicates. Keywords: Multimodal Logic, Embedded Implication, Translation. 1 Introduction Modal logics are widely used in computer science and artificial intelligence to deal with knowledge and beliefs, time, actions, and several researchers have proposed modal extensions of logic programming languages [7, 1, 13, 19, 17, 6]. In particular, in [5] we have defined a modal logic programming language which allows both multiple modalities and embedded implications. The language has been shown to be well suit...

Issues concerning the implementation of a notion of modules in the higher-order logic programming language Prolog are examined. A program in this language is a composite of type declarations and procedure definitions. The module construct that is considered permits large collections of such declarations and definitions to be decomposed into smaller units. Mechanisms are provided for controlling the interaction of these units and for restricting the visibility of names used within any unit. The typical interaction between modules has both a static and a dynamic nature. The parsing of expressions in a module might require declarations in a module that it interacts with, and this information must be available during compilation. Procedure definitions within a module might utilize procedures presented in other modules and support must be provided for making the appropriate invocation during execution. Our concern here is largely with the dynamic aspects of module interaction. We describe a...

There have been several proposals for logic programming language based on linear logic: Lolli [6], Lygon [5], LO [3], LinLog [2], Forum [8]. In addition, BinProlog allows the use of linear implications of affine logic (a variant of linear logic) [12, 13]. In these languages, it is possible to create and consume resources dynamically as logical formulas. The efficient handling of resource formulas is therefore an important issue in the implementation of these languages. In [10], N. Tamura and Y. Kaneda proposed an abstract machine called LLPAM which is an extension of the standard WAM [14, 1] for a linear logic programming language called LLP. LLP is a superset of Prolog and a subset of Lolli. However, in the original LLPAM design, a resource formula was stored as a term in a heap memory and was not compiled into LLPAM code. In this paper, we describe an extension of LLPAM for compiling resource formulas. In our extension, resources are compiled into closures which consist of...