Debugging and Termination
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Artículos en la categoría Debugging and Termination publicados en las Actas de las XV Jornadas de Programación y Lenguajes (PROLE 2015).
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Artículo A Declarative Debugger for Concurrent Erlang ProgramsCaballero, Rafael; Martin-Martin, Enrique; Riesco, Adrián; Tamarit, Salvador. Actas de las XV Jornadas de Programación y Lenguajes (PROLE 2015), 2015-09-15.Erlang is a concurrent language with features such as actor model concurrency, no shared memory, message passing communication, high scalability and availability. However, the development of concurrent programs is a complex and error prone task. In this paper we present a declarative debugging approach for concurrent Erlang programs. Our debugger asks questions about the validity of transitions between the different points of the program that involve message passing and/or process creation. The answers, which represent the intended behavior of the program, are compared with the transitions obtained in an actual execution of the program. The differences allow us to detect program errors and to point out the pieces of source code responsible for the bugs. In order to represent the computations we present a semantic calculus for concurrent Core Erlang programs. The debugger uses the proof trees in this calculus as debugging trees used for selecting the questions asked to the user. The relation between the debugging trees and the semantic calculus allows us to establish the soundness of the approach. The theoretical ideas have been implemented in a debugger prototype.Resumen Thresholded Debugging of XPath QueriesAlmendros-Jiménez, Jesus M.; Luna, Alejandro; Moreno, Ginés. Actas de las XV Jornadas de Programación y Lenguajes (PROLE 2015), 2015-09-15.We have recently designed/implemented a method for debugging Fuzzy-XPath queries which produces a set of alternative Fuzzy-XPath expressions with higher chances for retrieving answers from XML files. The main goal of the present paper consists in the introduction of a new fuzzy command inside the Fuzzy-XPath debugger which comfortably relies on our implementation based on fuzzy logic programming. So, when <<[FILTER=r]>> precedes a fuzzy query the debugger lazily explores an input XML document for dynamically disregarding as soon as possible those branches of the XML tree leading to irrelevant solutions (i.e., with a chance degree degraded below r), thus allowing the possibility of efficiently managing large files without reducing the set of answers for which users are mainly interested in. Hence, advice that this dynamic thresholding technique embedded into the core of the Fuzzy-XPath debugger has two advantages: • firstly it permits to concentrate on significant answers (i.e., alternative queries which do not excessively deviate from the original one) without disturbing the attention with useless information, and • secondly, the computational behavior of the debugging process is highly improved (both in time and space) since a great amount of work is avoided when discriminating useless branches of the XML tree.Artículo Productivity of rewrite systems without transformationsLucas, Salvador. Actas de las XV Jornadas de Programación y Lenguajes (PROLE 2015), 2015-09-15.Termination of programs, i.e., the absence of infinite computations, ensures the existence of normal forms for all initial expressions, thus providing an essential ingredient for the definition of a normalization semantics for functional programs. In lazy functional languages, though, infinite data structures are often delivered as the outcome of computations. For instance, the list of all prime numbers can be returned as a neverending stream of numerical expressions or data structures. If such streams are allowed, requiring termination is hopeless. In this setting, the notion of productivity can be used to provide an account of computations with infinite data structures, as it “captures the idea of computability, of progress of infinite-list programs” (B.A. Sijtsma, On the Productivity of Recursive List Definitions, ACM Transactions on Programming Languages and Systems 11(4):633- 649, 1989). However, in the realm of Term Rewriting Systems, which can be seen as (first-order, untyped, unconditional) functional programs, termination of Context-Sensitive Rewriting (CSR) has been showed equivalent to productivity of rewrite systems through appropriate transformations. In this way, tools for proving termination of CSR can be used to prove productivity. In term rewriting, CSR is the restriction of rewriting that arises when reductions are allowed on selected arguments of function symbols only. In this paper we show that well-known results about the computational power or CSR are useful to better understand the existing connections between productivity of rewrite systems and termination of CSR, and also to obtain more powerful techniques to prove productivity of rewrite systems.