Revisiting logical semantics for processes and their distances

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Informática, Departamento de Sistemas Informáticos y Computación, leída el 2-02-2016Esta tesis se enmarca en el amplio campo de la teoría de la concurrencia. Más específicamente, nos centramos en el estudio de las relaciones de similitud entre procesos concurrentes. Comenzamos estudiando la bisimulación, considerada la más importante de estas relaciones, y vemos después cómo podemos extender nuestros resultados al resto de las semánticas de procesos estudiadas durante las últimas décadas. En particular, nuestra contribución a la comunidad científica, se centra en dos puntos principales: – El desarrollo de una caracterización lógica uniforme de las semánticas de procesos: proponemos un esquema lógico común (enmarcado en la conocida lógica modal de Hennessy-Milner) e incluimos las diferentes semánticas en este esquema, enfatizando las diferencias y similitudes entre ellas, que se presentan del modo más claro posible. – La presentación de una nueva noción de distancia, tanto entre procesos finitos como infinitos: la misma se diferencia de las anteriormente propuestas en su carácter global, que acumula las diferencias que aportan los distintos cómputos, en lugar de quedarnos con la máxima de ellas...This thesis can be included in the broad field of concurrency theory. More specifically, we focus on the study of the similarities between concurrent processes. We start from bisimulation, the main of these relations, and then we see how we can extend the obtained results to the rest of the semantics developed along the last years. In particular, our main contributions can be roughly described by the following two items: – The development of a unified logical characterization of process semantics: we propose a common logical scheme (within the framework of the well known Hennessy-Milner Logic) and we set the different semantics in this scheme by emphasizing, in the clearest possible way, the (dis)similarities between them. – We present a new notion of distance for both finite and infinite processes. This novel notion differs from the previously available ones in its global character: instead of taking the maximum disagreement between the two compared processes, it adds all the differences provided by their whole sets of computations...Depto. de Sistemas Informáticos y ComputaciónFac. de InformáticaTRUEunpu

Probabilistic Process Algebra

Every day we witness the fast development of the hardware and software technology. This, of course, is the reason that new and more complex systems controlled by some kind of computational-based devices become an unseparated part of our daily life. As more as the system complexity increases, as more the reasoning about its correct behaviour becomes dif??cult. A variety of consequences may occur as a result of a failure, ranging from simple annoying to life threatening ones. Thus for some systems it is crucial that they exhibit a correct functioning. However, for systems with an extremely complex construction it is almost impossible to give an absolute guarantee for their correctness. In this case, it is still satisfactory to know that the possibility for a system to fail is low enough. Formal methods have been developed for establishing correctness of computer systems. They provide rigorous methods with which one can formally specify properties of a systems's intended behaviour, and also can check if the system conforms to that speci??cation. In case of complex systems we need a formal method that allows us to reason in compositional way, it provides us with techniques that can be used to build larger systems from the composition of smaller ones. Process algebra carries exactly this idea; it provides operators that allow to compose processes in order to obtain a more complex process. Besides, every process algebra contains a set of axioms. Every axiom is an algebraic equation that carries our intuition and insight in process behaviour, it expresses which two processes behaviour we consider equal. In such a way, manipulation with processes becomes manipulation with equations in the algebraic sense. But, equations and operators do not have any meaning unless we place them in a certain real ¿world¿ and match the terms of the process algebra with the entities of the real world. This step is traditionally called ¿giving a semantic of the syntax¿. The structure constructed in this way is called a model of the considered process algebra. For every given process algebra we can construct an in??nite number of models, but only several of them are interesting for the purpose process algebra was developed as a formal method. However, there is a tendency always to use so-called a bisimulation model. In this thesis we propose several process algebras and construct their models based on the notion of bisimulation

Static analysis of unbounded structures in object-oriented programs

In this thesis we investigate different techniques and formalisms to address complexity introduced by unbounded structures in object-oriented programs. We give a representation of a weakest precondition calculus for abstract object creation in dynamic logic. Based on this calculus we define symbolic execution including abstract object creation. We investigate the complex behaviour introduced by multi-threading and give a formalism based on the transformation of multi-threaded reentrant call-graphs to thread automata and the application of context free language reachability to decide deadlock freedom of such programs. We give a formalisation of the observable interface behaviour of a concurrent, object-oriented language with futures and promises. The calculus captures the core of the Creol language and allows for a comparison with the concurrency model of thread-based, object-oriented languages like Java or C#. We give a technique to detect deadlock freedom for an Actor-like subset of the Creol language. LEI Universiteit LeidenThe work in this thesis has been carried out at the Christian-Albrechts--Universität zu Kiel, the Centrum Wiskunde & Informatica (CWI), and the Universiteit Leiden. The research was partially funded by the EU-project IST- 33826 Credo: Modeling and analysis of evolutionary structures for distributed services; the EU-project FP7-231620 HATS: Highly Adaptable and Trustworthy Software using Formal Methods; and the German-Norwegian DAAD-NWO exchange project Avabi (Automated validation for behavioral interfaces of asynchronous active objects).Algorithms and the Foundations of Software technolog