Declarative Debugging of Missing Answers for Maude

Declarative debugging is a semi-automatic technique that starts from an incorrect computation and locates a program fragment responsible for the error by building a tree representing this computation and guiding the user through it to find the error. Membership equational logic (MEL) is an equational logic that in addition to equations allows the statement of membership axioms characterizing the elements of a sort. Rewriting logic is a logic of change that extends MEL by adding rewrite rules, that correspond to transitions between states and can be nondeterministic. In this paper we propose a calculus that allows to infer normal forms and least sorts with the equational part, and sets of reachable terms through rules. We use an abbreviation of the proof trees computed with this calculus to build appropriate debugging trees for missing answers (results that are erroneous because they are incomplete), whose adequacy for debugging is proved. Using these trees we have implemented a declarative debugger for Maude, a high-performance system based on rewriting logic, whose use is illustrated with an example

Debugging Maude programs via runtime assertion checking and trace slicing

[EN] This is the author’s version of a work that was accepted for publication in . Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Logical and Algebraic Methods in Programming, [VOL 85, ISSUE 5, (2016)] DOI 10.1016/j.jlamp.2016.03.001.In this paper we propose a dynamic analysis methodology for improving the diagnosis of erroneous Maude programs. The key idea is to combine runtime checking and dynamic trace slicing for automatically catching errors at runtime while reducing the size and complexity of the erroneous traces to be analyzed (i.e., those leading to states failing to satisfy some of the assertions). First, we formalize a technique that is aimed at automatically detecting deviations of the program behavior (symptoms) with respect to two types of user-defined assertions: functional assertions and system assertions. The proposed dynamic checking is provably sound in the sense that all errors flagged are definitely violations of the specifications. Then, upon eventual assertion violations we generate accurate trace slices that help identify the cause of the error. Our methodology is based on (i) a logical notation for specifying assertions that are imposed on execution runs; (ii) a runtime checking technique that dynamically tests the assertions; and (iii) a mechanism based on (equational) least general generalization that automatically derives accurate criteria for slicing from falsified assertions. Finally, we report on an implementation of the proposed technique in the assertion-based, dynamic analyzer ABETS and show how the forward and backward tracking of asserted program properties leads to a thorough trace analysis algorithm that can be used for program diagnosis and debugging. © 2016 Elsevier Inc. All rights reserved.This work has been partially supported by the EU (FEDER) and the Spanish MINECO under grants TIN2015-69175-C4-1-R and TIN2013-45732-C4-1-P, and by Generalitat Valenciana Ref. PROMETEOII/2015/013. F. Frechina was supported by FPU-ME grant AP2010-5681, and J. Sapiña was supported by FPI-UPV grant SP2013-0083 and mobility grant VIIT-3946.Alpuente Frasnedo, M.; Ballis, D.; Frechina, F.; Sapiña-Sanchis, J. (2016). Debugging Maude programs via runtime assertion checking and trace slicing. Journal of Logical and Algebraic Methods in Programming. 85(5):707-736. https://doi.org/10.1016/j.jlamp.2016.03.001S70773685

Combining Runtime Checking and Slicing to Improve Maude Error Diagnosis

The final publication is available at Springer via http://dx.doi.org/10.1007/978-3-319-23165-5_3This paper introduces the idea of using assertion checking for enhancing the dynamic slicing of Maude computation traces. Since trace slicing can greatly simplify the size and complexity of the analyzed traces, our methodology can be useful for improving the diagnosis of erroneous Maude programs. The proposed methodology is based on (i) a logical notation for specifying two types of user-defined assertions that are imposed on execution runs: functional assertions and system assertions; (ii) a runtime checking technique that dynamically tests the assertions and is provably safe in the sense that all errors flagged are definite violations of the specifications; and (iii) a mechanism based on equational least general generalization that automatically derives accurate criteria for slicing from falsified assertions.This work has been partially supported by the EU (FEDER) and the Spanish MINECO project ref. TIN2013-45732-C4-01 (DAMAS), and by Generalitat Valenciana ref. PROMETEOII/2015/013 (SmartLogic). F. Frechina was supported by FPU-ME grant AP2010-5681, and J. Sapiña was supported by FPI-UPV grant SP2013-0083.Alpuente Frasnedo, M.; Ballis, D.; Frechina Navarro, F.; Sapiña Sanchis, J. (2015). Combining Runtime Checking and Slicing to Improve Maude Error Diagnosis. En Logic, Rewriting, and Concurrency. Essays Dedicated to José Meseguer on the Occasion of His 65th Birthday. 72-96. https://doi.org/10.1007/978-3-319-23165-5_3S7296Alpuente, M., Ballis, D., Espert, J., Romero, D.: Backward trace slicing for rewriting logic theories. In: Bjørner, N., Sofronie-Stokkermans, V. (eds.) CADE 2011. LNCS, vol. 6803, pp. 34–48. Springer, Heidelberg (2011)Alpuente, M., Ballis, D., Frechina, F., Romero, D.: Backward trace slicing for conditional rewrite theories. In: Bjørner, N., Voronkov, A. (eds.) LPAR-18 2012. LNCS, vol. 7180, pp. 62–76. Springer, Heidelberg (2012)Alpuente, M., Ballis, D., Frechina, F., Romero, D.: Julienne: a trace slicer for conditional rewrite theories. In: Giannakopoulou, D., Méry, D. (eds.) FM 2012. LNCS, vol. 7436, pp. 28–32. Springer, Heidelberg (2012)Alpuente, M., Ballis, D., Frechina, F., Romero, D.: Using conditional trace slicing for improving Maude programs. Sci. Comput. Program. 80, Part B:385–415 (2014)Alpuente, M., Ballis, D., Frechina, F., Sapiña, J.: Slicing-based trace analysis of rewriting logic specifications with $$I$$ Julienne. In: Felleisen, M., Gardner, P. (eds.) ESOP 2013. LNCS, vol. 7792, pp. 121–124. Springer, Heidelberg (2013)Alpuente, M., Ballis, D., Frechina, F., Sapiña, J.: Inspecting rewriting logic computations (in a Parametric and Stepwise Way). In: Iida, S., Meseguer, J., Ogata, K. (eds.) Specification, Algebra, and Software. LNCS, vol. 8373, pp. 229–255. Springer, Heidelberg (2014)Alpuente, M., Ballis, D., Frechina, F., Sapiña, J.: Debugging Maude programs via runtime assertion checking and trace slicing. Technical report, Department of Computer Systems and Computation, Universitat Politècnica de València (2015). http://safe-tools.dsic.upv.es/abets/abets-tr.pdfAlpuente, M., Ballis, D., Frechina, F., Sapiña, J.: Exploring conditional rewriting logic computations. J. Symbolic Comput. 69, 3–39 (2015)Alpuente, M., Escobar, S., Espert, J., Meseguer, J.: A modular order-sorted equational generalization algorithm. Inf. Comput. 235, 98–136 (2014)Baader, F., Snyder, W.: Unification Theory. In: Robinson, J.A., Voronkov, A. (eds.) Handbook of Automated Reasoning, vol. I, pp. 447–533. Elsevier Science (2001)Bruni, R., Meseguer, J.: Semantic foundations for generalized rewrite theories. Theor. Comput. Sci. 360(1–3), 386–414 (2006)Clarke, L.A., Rosenblum, D.S.: A historical perspective on runtime assertion checking in software development. ACM SIGSOFT Softw. Eng. Notes 31(3), 25–37 (2006)Clavel, M., Durán, F., Eker, S., Lincoln, P., Martí-Oliet, N., Meseguer, J., Talcott, C.: All About Maude - A High-Performance Logical Framework. LNCS. Springer, Heidelberg (2007)Clavel, M., Durán, F., Eker, S., Lincoln, P., Martí-Oliet, N., Meseguer, J., Talcott, C.: Maude Manual (Version 2.6). Technical report, SRI International Computer Science Laboratory (2011). http://maude.cs.uiuc.edu/maude2-manual/Durán, F., Meseguer, J.: A Maude coherence checker tool for conditional order-sorted rewrite theories. In: Ölveczky, P.C. (ed.) WRLA 2010. LNCS, vol. 6381, pp. 86–103. Springer, Heidelberg (2010)Durán, F., Roldán, M., Vallecillo, A.: Invariant-driven strategies for Maude. Electron. Notes Theor. Comput. Sci. 124(2), 17–28 (2005)Goguen, J.A., Meseguer, J.: Equality, types, modules, and (why not?) generics for logic programming. J. Logic Program. 1(2), 179–210 (1984)Goguen, J.A., Meseguer, J.: Unifying functional, object-oriented and relational programming with logical semantics. In: Agha, G., Wegner, P., Yonezawa, A. (eds.), Research Directions in Object-Oriented Programming, pp. 417–478. The MIT Press (1987)Klop, J.W.: Term rewriting systems. In: Abramsky, S., Gabbay, D., Maibaum, T. (eds.), Handbook of Logic in Computer Science, vol. I, pp. 1–112. Oxford University Press (1992)Korel, B., Laski, J.: Dynamic program slicing. Inf. Process. Lett. 29(3), 155–163 (1988)Lassez, J.L., Maher, M.J., Marriott, K.: Unification Revisited. In: Minker, J. (ed.) Foundations of Deductive Databases and Logic Programming, pp. 587–625. Morgan Kaufmann, Los Altos, California (1988)Leavens, G.T., Cheon, Y.: Design by Contract with JML (2005). http://www.eecs.ucf.edu/ leavens/JML/jmldbc.pdfMartí-Oliet, N., Palomino, M., Verdejo, A.: Rewriting logic bibliography by topic: 1990–2011. J. Logic Algebraic Program. 81(7–8), 782–815 (2012)Meseguer, J.: Conditional rewriting logic as a unified model of concurrency. Theoret. Comput. Sci. 96(1), 73–155 (1992)Meseguer, J.: Multiparadigm logic programming. In: Kirchner, H., Levi, G. (eds.) ALP 1992. LNCS, vol. 632, pp. 158–200. Springer, Heidelberg (1992)Rocha, C., Meseguer, J., Muñoz, C.: Rewriting modulo SMT and open system analysis. In: Escobar, S. (ed.) WRLA 2014. LNCS, vol. 8663, pp. 247–262. Springer, Heidelberg (2014)Roşu, G.: From Rewriting Logic, to Programming Language Semantics, to Program Verification. In: Martí-Oliet, N., Ölveczky, P.C., Talcott, C., (eds.) Logic, Rewriting, and Concurrency. LNCS, vol. 9200, pp. 598–616. Springer, Heidelberg (2015)Roldán, M., Durán, F., Vallecillo, A.: Invariant-driven specifications in Maude. Sci. Comput. Program. 74(10), 812–835 (2009)TeReSe. Term Rewriting Systems. Cambridge University Press (2003

Rewriting Logic Techniques for Program Analysis and Optimization

Esta tesis propone una metodología de análisis dinámico que mejora el diagnóstico de programas erróneos escritos en el lenguaje Maude. La idea clave es combinar técnicas de verificación de aserciones en tiempo de ejecución con la fragmentación dinámica de trazas de ejecución para detectar automáticamente errores en tiempo de ejecución, al tiempo que se reduce el tamaño y la complejidad de las trazas a analizar. En el caso de violarse una aserción, se infiere automáticamente el criterio de fragmentación, lo que facilita al usuario identificar rápidamente la fuente del error. En primer lugar, la tesis formaliza una técnica destinada a detectar automáticamente eventuales desviaciones del comportamiento deseado del programa (síntomas de error). Esta técnica soporta dos tipos de aserciones definidas por el usuario: aserciones funcionales (que restringen llamadas a funciones deterministas) y aserciones de sistema (que especifican los invariantes de estado del sistema). La técnica de verificación dinámica propuesta es demostrablemente correcta en el sentido de que todos los errores señalados definitivamente delatan la violación de las aserciones. Tras eventuales violaciones de aserciones, se generan automáticamente trazas fragmentadas (es decir, trazas simplificadas pero igualmente precisas) que ayudan a identificar la causa del error. Además, la técnica también sugiere una posible reparación para las reglas implicadas en la generación de los estados erróneos. La metodología propuesta se basa en (i) una notación lógica para especificar las aserciones que se imponen a la ejecución; (ii) una técnica de verificación aplicable en tiempo de ejecución que comprueba dinámicamente las aserciones; y (iii) un mecanismo basado en la generalización (ecuacional) menos general que automáticamente obtiene criterios precisos para fragmentar trazas de ejecución a partir de aserciones falsificadas. Por último, se presenta una implementación de la técnica propuesta en la herramienta de análisis dinámico basado en aserciones ABETS, que muestra cómo es posible combinar el trazado de las propiedades asertadas del programa para obtener un algoritmo preciso de análisis de trazas que resulta útil para el diagnóstico y la depuración de programas.This thesis proposes a dynamic analysis methodology for improving the diagnosis of erroneous Maude programs. The key idea is to combine runtime assertion checking and dynamic trace slicing for automatically catching errors at runtime while reducing the size and complexity of the erroneous traces to be analyzed (i.e., those leading to states that fail to satisfy the assertions). In the event of an assertion violation, the slicing criterion is automatically inferred, which facilitates the user to rapidly pinpoint the source of the error. First, a technique is formalized that aims at automatically detecting anomalous deviations of the intended program behavior (error symptoms) by using assertions that are checked at runtime. This technique supports two types of user-defined assertions: functional assertions (which constrain deterministic function calls) and system assertions (which specify system state invariants). The proposed dynamic checking is provably sound in the sense that all errors flagged definitely signal a violation of the specifications. Then, upon eventual assertion violations, accurate trace slices (i.e., simplified yet precise execution traces) are generated automatically, which help identify the cause of the error. Moreover, the technique also suggests a possible repair for the rules involved in the generation of the erroneous states. The proposed methodology is based on (i) a logical notation for specifying assertions that are imposed on execution runs; (ii) a runtime checking technique that dynamically tests the assertions; and (iii) a mechanism based on (equational) least general generalization that automatically derives accurate criteria for slicing from falsified assertions. Finally, an implementation of the proposed technique is presented in the assertion-based, dynamic analyzer ABETS, which shows how the forward and backward tracking of asserted program properties leads to a thorough trace analysis algorithm that can be used for program diagnosis and debugging.Esta tesi proposa una metodologia d'anàlisi dinàmica que millora el diagnòstic de programes erronis escrits en el llenguatge Maude. La idea clau és combinar tècniques de verificació d'assercions en temps d'execució amb la fragmentació dinàmica de traces d'execució per a detectar automàticament errors en temps d'execució, alhora que es reduïx la grandària i la complexitat de les traces a analitzar. En el cas de violar-se una asserció, s'inferix automàticament el criteri de fragmentació, la qual cosa facilita a l'usuari identificar ràpidament la font de l'error. En primer lloc, la tesi formalitza una tècnica destinada a detectar automàticament eventuals desviacions del comportament desitjat del programa (símptomes d'error). Esta tècnica suporta dos tipus d'assercions definides per l'usuari: assercions funcionals (que restringixen crides a funcions deterministes) i assercions de sistema (que especifiquen els invariants d'estat del sistema). La tècnica de verificació dinàmica proposta és demostrablement correcta en el sentit que tots els errors assenyalats definitivament delaten la violació de les assercions. Davant eventuals violacions d'assercions, es generen automàticament traces fragmentades (és a dir, traces simplificades però igualment precises) que ajuden a identificar la causa de l'error. A més, la tècnica també suggerix una possible reparació de les regles implicades en la generació dels estats erronis. La metodologia proposada es basa en (i) una notació lògica per a especificar les assercions que s'imposen a l'execució; (ii) una tècnica de verificació aplicable en temps d'execució que comprova dinàmicament les assercions; i (iii) un mecanisme basat en la generalització (ecuacional) menys general que automàticament obté criteris precisos per a fragmentar traces d'execució a partir d'assercions falsificades. Finalment, es presenta una implementació de la tècnica proposta en la ferramenta d'anàlisi dinàmica basat en assercions ABETS, que mostra com és possible combinar el traçat cap avant i cap arrere de les propietats assertades del programa per a obtindre un algoritme precís d'anàlisi de traces que resulta útil per al diagnòstic i la depuració de programes.Sapiña Sanchis, J. (2017). Rewriting Logic Techniques for Program Analysis and Optimization [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/94044TESI

Explanation of the Model Checker Verification Results

Immer wenn neue Anforderungen an ein System gestellt werden, müssen die Korrektheit und Konsistenz der Systemspezifikation überprüft werden, was in der Praxis in der Regel manuell erfolgt. Eine mögliche Option, um die Nachteile dieser manuellen Analyse zu überwinden, ist das sogenannte Contract-Based Design. Dieser Entwurfsansatz kann den Verifikationsprozess zur Überprüfung, ob die Anforderungen auf oberster Ebene konsistent verfeinert wurden, automatisieren. Die Verifikation kann somit iterativ durchgeführt werden, um die Korrektheit und Konsistenz des Systems angesichts jeglicher Änderung der Spezifikationen sicherzustellen. Allerdings ist es aufgrund der mangelnden Benutzerfreundlichkeit und der Schwierigkeiten bei der Interpretation von Verifizierungsergebnissen immer noch eine Herausforderung, formale Ansätze in der Industrie einzusetzen. Stellt beispielsweise der Model Checker bei der Verifikation eine Inkonsistenz fest, generiert er ein Gegenbeispiel (Counterexample) und weist gleichzeitig darauf hin, dass die gegebenen Eingabespezifikationen inkonsistent sind. Hier besteht die gewaltige Herausforderung darin, das generierte Gegenbeispiel zu verstehen, das oft sehr lang, kryptisch und komplex ist. Darüber hinaus liegt es in der Verantwortung der Ingenieurin bzw. des Ingenieurs, die inkonsistente Spezifikation in einer potenziell großen Menge von Spezifikationen zu identifizieren. Diese Arbeit schlägt einen Ansatz zur Erklärung von Gegenbeispielen (Counterexample Explanation Approach) vor, der die Verwendung von formalen Methoden vereinfacht und fördert, indem benutzerfreundliche Erklärungen der Verifikationsergebnisse der Ingenieurin bzw. dem Ingenieur präsentiert werden. Der Ansatz zur Erklärung von Gegenbeispielen wird mittels zweier Methoden evaluiert: (1) Evaluation anhand verschiedener Anwendungsbeispiele und (2) eine Benutzerstudie in Form eines One-Group Pretest-Posttest Experiments.Whenever new requirements are introduced for a system, the correctness and consistency of the system specification must be verified, which is often done manually in industrial settings. One viable option to traverse disadvantages of this manual analysis is to employ the contract-based design, which can automate the verification process to determine whether the refinements of top-level requirements are consistent. Thus, verification can be performed iteratively to ensure the system’s correctness and consistency in the face of any change in specifications. Having said that, it is still challenging to deploy formal approaches in industries due to their lack of usability and their difficulties in interpreting verification results. For instance, if the model checker identifies inconsistency during the verification, it generates a counterexample while also indicating that the given input specifications are inconsistent. Here, the formidable challenge is to comprehend the generated counterexample, which is often lengthy, cryptic, and complex. Furthermore, it is the engineer’s responsibility to identify the inconsistent specification among a potentially huge set of specifications. This PhD thesis proposes a counterexample explanation approach for formal methods that simplifies and encourages their use by presenting user-friendly explanations of the verification results. The proposed counterexample explanation approach identifies and explains relevant information from the verification result in what seems like a natural language statement. The counterexample explanation approach extracts relevant information by identifying inconsistent specifications from among the set of specifications, as well as erroneous states and variables from the counterexample. The counterexample explanation approach is evaluated using two methods: (1) evaluation with different application examples, and (2) a user-study known as one-group pretest and posttest experiment

Mathematics in Software Reliability and Quality Assurance

This monograph concerns the mathematical aspects of software reliability and quality assurance and consists of 11 technical papers in this emerging area. Included are the latest research results related to formal methods and design, automatic software testing, software verification and validation, coalgebra theory, automata theory, hybrid system and software reliability modeling and assessment

A program slicing method for a wide spectrum language

This thesis describes the implementation of a program slicer for WSL - a Wide Spectrum Language - which is a language that allows different levels of abstraction to coexist in the same program. WSL contains constructs not found in conventional languages, e.g. action systems (which model a segment of code with GOTOs and labels) and non deterministic constructs. Program slicing is a method for restricting a program to a specified behaviour of interest. Usually this behaviour of interest is expressed in terms of a variable or a set of variables. The method used in the thesis to slice a program is different from the classical ones in that slices do not need to be computed from an output statement, and in that slices are computed on a wide spectrum language closer to a functional language, instead of being computed on a more conventional, procedural language. A slicer for a subset of WSL has been designed and implemented based on the data flow analysis techniques for while-programs of Bergeretti and Carré [10]. It has been necessary to modify the algorithm to permit incremental slicing. Modifications of their algorithm were also needed to accommodate the specific WSL constructs mentioned above. The implementation has been developed using a rapid prototyping approach. The prototype has provided new ideas and enhancements for a more comprehensive sheer which could be implemented in the future. The slicer has assisted the maintainer using ReForm - a reverse engineering project developed at Durham University - in understanding and debugging a program by decomposing it. At the end of this thesis results showing how slicing has helped the maintainer are presented. Conclusions on the method used, the validity of the tool, and its engineering are also summarized

Optimization Techniques for Algorithmic Debugging

[EN] Nowadays, undetected programming bugs produce a waste of billions of dollars per year to private and public companies and institutions. In spite of this, no significant advances in the debugging area that help developers along the software development process have been achieved yet. In fact, the same debugging techniques that were used 20 years ago are still being used now. Along the time, some alternatives have appeared, but there still is a long way for them to be useful enough to get into the software development process. One of them is algorithmic debugging, which abstracts the information the user has to investigate to debug the program, allowing them to focus on what is happening instead of how it is happening. This abstraction comes at a price: the granularity level of the bugs that can be detected allows for isolating wrongly implemented functions, but which part of them contains the bug cannot be found out yet. This thesis focusses on improving algorithmic debugging in many aspects. Concretely, the main aims of this thesis are to reduce the time the user needs to detect a programming bug as well as to provide the user with more detailed information about where the bug is located. To achieve these goals, some techniques have been developed to start the debugging sessions as soon as possible, to reduce the number of questions the user is going to be asked about, and to augment the granularity level of those bugs that algorithmic debugging can detect, allowing the debugger in this way to keep looking for bugs even inside functions. As a result of this thesis, three completely new techniques have been defined, an already existent technique has been improved, and two new algorithmic debugging search strategies have been defined that improve the already existent ones. Besides these theoretical results, a fully functional algorithmic debugger has been implemented that contains and supports all these techniques and strategies. This debugger is written in Java, and it debugs Java code. The election of this language is justified because it is currently one of the most widely extended and used languages. Also because it contains an interesting combination of unsolved challenges for algorithmic debugging. To further increase its usability, the debugger has been later adapted as an Eclipse plugin, so it could be used by a wider number of users. These two debuggers are publicly available, so any interested person can access them and continue with the research if they wish so.[ES] Hoy en día, los errores no detectados de programación suponen un gasto de miles de millones al año para las empresas e instituciones públicas y privadas. A pesar de esto, no ha habido ningún avance significativo en el área de la depuración que ayude a los desarrolladores durante la fase de desarrollo de software. De hecho, las mismas técnicas de depuración que se utilizaban hace 20 años se siguen utilizando ahora. A lo largo del tiempo, han surgido algunas alternativas, pero todavía queda un largo camino para que estas sean lo suficientemente útiles como para abrirse camino en el proceso de desarrollo de software. Una de ellas es la depuración algorítmica, la cual abstrae la información que el programador debe investigar para depurar el programa, permitiéndole de este modo centrarse en el qué está ocurriendo en vez de en el cómo. Esta abstracción tiene un coste: el nivel de granularidad de los errores que pueden detectarse nos permite como máximo aislar funciones mal implementadas, pero no averiguar qué parte de estas contiene el error. Esta tesis se centra en mejorar la depuración algorítmica en muchos aspectos. Concretamente, los principales objetivos de esta tesis son reducir el tiempo que el usuario necesita para detectar un error de programación así como proporcionar información más detallada de dónde se encuentra el error. Para conseguir estos objetivos, se han desarrollado técnicas para iniciar las sesiones de depuración lo antes posible, reducir el número de preguntas que se le van a realizar al usuario, y aumentar el nivel de granularidad de los errores que la depuración algorítmica puede detectar, permitiendo así seguir buscando el error incluso dentro de las funciones. Como resultado de esta tesis, se han definido tres técnicas completamente nuevas, se ha mejorado una técnica ya existente, y se han definido dos nuevas estrategias de depuración algorítmica que mejoran las previamente existentes. Además de los resultados teóricos, también se ha desarrollado un depurador algorítmico completamente funcional que contiene y respalda todas estas técnicas y estrategias. Este depurador está escrito en Java y depura código Java. La elección de este lenguaje se justifica debido a que es uno de los lenguajes más ampliamente extendidos y usados actualmente. También debido a que contiene una combinación interesante de retos todavía sin resolver para la depuración algorítmica. Para aumentar todavía más su usabilidad, el depurador ha sido posteriormente adaptado como un plugin de Eclipse, de tal manera que pudiese ser usado por un número más amplio de usuarios. Estos dos depuradores están públicamente disponibles para que cualquier persona interesada pueda acceder a ellos y continuar con la investigación si así lo deseara.[CA] Hui en dia, els errors no detectats de programació suposen una despesa de milers de milions a l'any per a les empreses i institucions públiques i privades. Tot i això, no hi ha hagut cap avanç significatiu en l'àrea de la depuració que ajude als desenvolupadors durant la fase de desenvolupament de programari. De fet, les mateixes tècniques de depuració que s'utilitzaven fa 20 anys es continuen utilitzant ara. Al llarg del temps, han sorgit algunes alternatives, però encara queda un llarg camí perquè estes siguen prou útils com per a obrir-se camí en el procés de desenvolupament de programari. Una d'elles és la depuració algorítmica, la qual abstrau la informació que el programador ha d'investigar per a depurar el programa, permetent-li d'esta manera centrar-se en el què està ocorrent en compte de en el com. Esta abstracció té un cost: el nivell de granularitat dels errors que poden detectar-se ens permet com a màxim aïllar funcions mal implementades, però no esbrinar quina part d'estes conté l'error. Esta tesi es centra a millorar la depuració algorítmica en molts aspectes. Concretament, els principals objectius d'esta tesi són reduir el temps que l'usuari necessita per a detectar un error de programació així com proporcionar informació més detallada d'on es troba l'error. Per a aconseguir estos objectius, s'han desenvolupat tècniques per a iniciar les sessions de depuració com més prompte millor, reduir el nombre de preguntes que se li formularan a l'usuari, i augmentar el nivell de granularitat dels errors que la depuració algorítmica pot detectar, permetent així continuar buscant l'error inclús dins de les funcions. Com resultat d'esta tesi, s'han definit tres tècniques completament noves, s'ha millorat una tècnica ja existent, i s'han definit dos noves estratègies de depuració algorítmica que milloren les prèviament existents. A més dels resultats teòrics, també s'ha desenvolupat un depurador algorítmic completament funcional que conté i protegix totes estes tècniques i estratègies. Este depurador està escrit en Java i depura codi Java. L'elecció d'este llenguatge es justifica pel fet que és un dels llenguatges més àmpliament estesos i usats actualment. També pel fet que conté una combinació interessant de reptes encara sense resoldre per a la depuració algorítmica. Per a augmentar encara més la seua usabilitat, el depurador ha sigut posteriorment adaptat com un plugin d'Eclipse, de tal manera que poguera ser usat per un nombre més ampli d'usuaris. Estos dos depuradors estan públicament disponibles perquè qualsevol persona interessada puga accedir a ells i continuar amb la investigació si així ho desitjara.Insa Cabrera, D. (2016). Optimization Techniques for Algorithmic Debugging [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/68506TESISPremios Extraordinarios de tesis doctorale