Semantics of Input-Consuming Logic Programs

Input-consuming programs are logic programs with an additional restriction on the selectability (actually, on the resolvability) of atoms. this class of programs arguably allows to model logic programs employing a dynamic selection rule and constructs such as delay declarations: as shown also in [5], a large number of them are actually input-consuming. \ud in this paper we show that - under some syntactic restrictions - the tex2html_wrap_inline117-semantics of a program is correct and fully abstract also for input-consuming programs. this allows us to conclude that for a large class of programs employing delay declarations there exists a model-theoretic semantics which is equivalent to the operational one

Classes of Terminating Logic Programs

Termination of logic programs depends critically on the selection rule, i.e. the rule that determines which atom is selected in each resolution step. In this article, we classify programs (and queries) according to the selection rules for which they terminate. This is a survey and unified view on different approaches in the literature. For each class, we present a sufficient, for most classes even necessary, criterion for determining that a program is in that class. We study six classes: a program strongly terminates if it terminates for all selection rules; a program input terminates if it terminates for selection rules which only select atoms that are sufficiently instantiated in their input positions, so that these arguments do not get instantiated any further by the unification; a program local delay terminates if it terminates for local selection rules which only select atoms that are bounded w.r.t. an appropriate level mapping; a program left-terminates if it terminates for the usual left-to-right selection rule; a program exists-terminates if there exists a selection rule for which it terminates; finally, a program has bounded nondeterminism if it only has finitely many refutations. We propose a semantics-preserving transformation from programs with bounded nondeterminism into strongly terminating programs. Moreover, by unifying different formalisms and making appropriate assumptions, we are able to establish a formal hierarchy between the different classes.Comment: 50 pages. The following mistake was corrected: In figure 5, the first clause for insert was insert([],X,[X]

Generating Efficient, Terminating Logic Programs

The objective of control generation in logic programming is to automatically derive a computation rule for a program that is efficient and yet does not compromise program correctness. Progress in solving this important problem has been slow and, to date, only partial solutions have been proposed where the generated programs are either incorrect or inefficient. We show how the control generation problem can be tackled with a simple automatic transformation that relies on information about the depths of derivations. To prove correctness of our transform we introduce the notion of a semi delay recurrent program which generalises previous ideas in the termination literature for reasoning about logic programs with dynamic selection rules

Smart test data generators via logic programming

We present a novel counterexample generator for the interactive theorem prover Isabelle based on a compiler that synthesizes test data generators for functional programming languages (e.g. Standard ML, OCaml) from specifications in Isabelle. In contrast to naive type-based test data generators, the smart generators take the preconditions into account and only generate tests that fulfill the preconditions. The smart generators are constructed by a compiler that reformulates the preconditions as logic programs and analyzes them by an enriched mode inference. From this inference, the compiler can construct the desired generators in the functional programming language. These test data generators are applied to find errors in specifications, as we show in a case study of a hotel key card system

Concolic Testing in Logic programming

Software testing is one of the most popular validation techniques in the software industry. Surprisingly, we can only find a few approaches to testing in the context of logic programming. In this paper, we introduce a systematic approach for dynamic testing that combines both concrete and symbolic execution. Our approach is fully automatic and guarantees full path coverage when it terminates. We prove some basic properties of our technique and illustrate its practical usefulness through a prototype implementation.This work has been partially supported by the EU (FEDER) and the Spanish Ministerio de Economia y Competitividad under grant TIN2013-44742-C4-1-R and by the Generalitat Valenciana under grant PROMETEOII/2015/013. Part of this research was done while the third author was visiting the University of Reunion; G. Vidal gratefully acknowledges their hospitality.Mesnard, F.; Payet, E.; Vidal Oriola, GF. (2015). Concolic Testing in Logic programming. Theory and Practice of Logic Programming. 15(4):711-725. https://doi.org/10.1017/S1471068415000332S711725154SCHIMPF, J., & SHEN, K. (2011). ECLiPSe – From LP to CLP. Theory and Practice of Logic Programming, 12(1-2), 127-156. doi:10.1017/s1471068411000469Martelli, A., & Montanari, U. (1982). An Efficient Unification Algorithm. ACM Transactions on Programming Languages and Systems, 4(2), 258-282. doi:10.1145/357162.357169Godefroid, P., Klarlund, N., & Sen, K. (2005). DART. Proceedings of the 2005 ACM SIGPLAN conference on Programming language design and implementation - PLDI ’05. doi:10.1145/1065010.1065036Mera E. , López-García P. , and Hermenegildo M. V. 2009. Integrating software testing and run-time checking in an assertion verification framework. In 25th International Conference on Logic Programming, ICLP 2009, Pasadena. 281–295.Godefroid, P., Levin, M. Y., & Molnar, D. (2012). SAGE. Communications of the ACM, 55(3), 40. doi:10.1145/2093548.2093564WIELEMAKER, J., SCHRIJVERS, T., TRISKA, M., & LAGER, T. (2011). SWI-Prolog. Theory and Practice of Logic Programming, 12(1-2), 67-96. doi:10.1017/s1471068411000494CARLSSON, M., & MILDNER, P. (2011). SICStus Prolog—The first 25 years. Theory and Practice of Logic Programming, 12(1-2), 35-66. doi:10.1017/s1471068411000482Degrave F. , Schrijvers T. , and Vanhoof W. 2008. Automatic generation of test inputs for Mercury. In Logic-Based Program Synthesis and Transformation, 18th International Symposium, LOPSTR 2008. 71–86.Somogyi, Z., Henderson, F., & Conway, T. (1996). The execution algorithm of mercury, an efficient purely declarative logic programming language. The Journal of Logic Programming, 29(1-3), 17-64. doi:10.1016/s0743-1066(96)00068-4Vidal, G. (2015). Concolic Execution and Test Case Generation in Prolog. Lecture Notes in Computer Science, 167-181. doi:10.1007/978-3-319-17822-6_10Belli F. and Jack O. 1993. Implementation-based analysis and testing of Prolog programs. In ISSTA. 70–80.King, J. C. (1976). Symbolic execution and program testing. Communications of the ACM, 19(7), 385-394. doi:10.1145/360248.360252Lloyd, J. W. (1987). Foundations of Logic Programming. doi:10.1007/978-3-642-83189-8Clarke L. 1976. A program testing system. In Proceedings of the 1976 Annual Conference (ACM'76). 488–491

Object-oriented data mining

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Language Interoperability and Logic Programming Languages

We discuss P#, our implementation of a tool which allows interoperation between a concurrent superset of the Prolog programming language and C#. This enables Prolog to be used as a native implementation language for Microsoft's .NET platform. P# compiles a linear logic extension of Prolog to C# source code. We can thus create C# objects from Prolog and use C#'s graphical, networking and other libraries. P# was developed from a modified port of the Prolog to Java translator, Prolog Cafe. We add language constructs on the Prolog side which allow concurrent Prolog code to be written. We add a primitive predicate which evaluates a Prolog structure on a newly forked thread. Communication between threads is based on the unification of variables contained in such a structure. It is also possible for threads to communicate through a globally accessible table. All of the new features are available to the programmer through new built-in Prolog predicates. We present three case studies. The first is an application which allows several users to modify a database. The users are able to disconnect from the database and to modify their own copies of the data before reconnecting. On reconnecting, conflicts must be resolved. The second is an object-oriented assistant, which allows the user to query the contents of a C# namespace or Java package. The third is a tool which allows a user to interact with a graphical display of the inheritance tree. Finally, we optimize P#'s runtime speed by translating some Prolog predicates into more idiomatic C# code than is produced by a naive port of Prolog Cafe. This is achieved by observing that semi-deterministic predicates (being those which always either fail or succeed with exactly one solution) that only call other semi-deterministic predicates enjoy relatively simple control flow. We make use of the fact that Prolog programs often contain predicates which operate as functions, and that such predicates are usually semi-deterministic