En sistemas de software críticos, tales como sistemas de control de vuelo de aviones o sistemas de control de ascensores, los errores de software deben ser evitados. En la actualidad, existen técnicas y herramientas para asegurar la correctitud de sistemas críticos, siendo “model checking” (chequeo de modelos) una de las más populares. Con model checking, tanto el sistema de software como las propiedades deseadas del sistema (seguridad, alcanzabilidad, etc.) se modelan utilizando lenguajes de especificación formal; es decir, lenguajes basados en conceptos lógicomatemáticos. Las propiedades son especificadas normalmente a través de un tipo de lógica denominada “lógica temporal”. Profundizando sobre dicha lógica, el presente trabajo muestra los aspectos epistemológicos relacionados, detallando sobre su origen y evolución, desde las nociones de lógicas introducidas por Aristóteles hasta su concepción como herramienta clave para la verificación de sistemas de software críticos.

Although cryptographic software implementation is often performed by expert programmers, the range of performance and security driven options, as well as more mundane software engineering issues, still make it a challenge. The use of domain specific language and compiler techniques to assist in description and optimisation of cryptographic software is an interesting research challenge. In this paper we investigate two aspects of such techniques, focusing on Elliptic Curve Cryptography (ECC) in particular. Our constructive results show that a suitable language allows description of ECC based software in a manner close to the original mathematics; the corresponding compiler allows automatic production of an executable whose performance is competitive with that of a hand-optimised implementation. In contrast, we study the worrying potential for naïve compiler driven optimisation to render cryptographic software insecure. Both aspects of our work are set within the context of CACE, an ongoing EU funded project on this general topic.

A transition system can be presented either as a binary relation or as a coalgebra for the powerset functor, each representation being obtained from the other by transposition. More generally, a coalgebra for a functor F generalises transition systems in the sense that a shape for transitions is determined by F, typically encoding a signature of methods and observers. This paper explores such a duality to frame in purely relational terms coalgebraic refinement, showing that relational (data) refinement of transition relations, in its two variants, downward and upward (functional) simulations, is equivalent to coalgebraic refinement based on backward and forward morphisms, respectively. Going deeper, it is also shown that downward simulation provides a complete relational rule to prove coalgebraic refinement. With such a single rule the paper defines a pre-ordered calculus for refinement of coalgebras, with bisimilarity as the induced equivalence. The calculus is monotonic with respect to the main relational operators and arbitrary relator F, therefore providing a framework for structural reasoning about refinement.

Service-oriented computing is an emerging paradigm with increasing impact on the way modern software systems are designed and developed. Services are autonomous, loosely coupled and heterogeneous computational entities able to cooperate to achieve common goals. This paper introduces a model for service orchestration, which combines a exogenous coordination model, with services’ interfaces annotated with behavioural patterns specified in a process algebra which is parametric on the interaction discipline. The coordination model is a variant of Reo for which a new semantic model is proposed.

Generating minimal hitting sets of a collection of sets is known to be NP-hard, necessitating heuristic approaches to handle large problems. In this paper a low-cost, approximate minimal hitting set (MHS) algorithm, coined Staccato, is presented. Staccato uses a heuristic function, borrowed from a lightweight, statistics-based software fault localization approach, to guide the MHS search. Given the nature of the heuristic function, Staccato is specially tailored to model-based diagnosis problems (where each MHS solution is a diagnosis to the problem), although well-suited for other application domains as well. We apply Staccato in the context of model-based diagnosis and show that even for small problems our approach is orders of magnitude faster than the brute-force approach, while still
capturing all important solutions. Furthermore, due to its low cost complexity, we also show that Staccato is amenable to large problems including millions of variables.

In focusing on human system interactions, the challenge for software engineers is to build systems that allow users to carry out activities and achieve objectives effectively and safely. A well-designed system should also provide a better experience of use, reducing stress and frustration. Many methods aim to help designers to produce systems that have these characteristics. Our research is concerned with the use of formal techniques to help construct such interactive systems.

Engineering natural and appropriate interactive behaviour in ubiquitous computing systems presents new challenges to their developers. This paper explores formal models of interactive behaviour in ubiquitous systems. Of particular interest is the way that these models may help engineers to visualise the consequences of different designs. Design options based on a dynamic signage system (GAUDI) are explored using different instances of a generic model of the system.