(Ω, Ξ)-Logic: On the Algebraic Extension of Coalgebraic Specifications

We present an extension of standard coalgebraic specification techniques for statebased systems which allows us to integrate constants and n-ary operations in a smooth way and, moreover, leads to a simplification of the coalgebraic structure of the models of a specification. The framework of (Ω,Ξ)-logic can be considered as the result of a translation of concepts of observational logic (cf. [9]) into the coalgebraic world. As a particular outcome we obtain the notion of an (Ω, Ξ)- structure and a sound and complete proof system for (first-order) observational properties of specifications

Control refinement for discrete-time descriptor systems: a behavioural approach via simulation relations

The analysis of industrial processes, modelled as descriptor systems, is often computationally hard due to the presence of both algebraic couplings and difference equations of high order. In this paper, we introduce a control refinement notion for these descriptor systems that enables analysis and control design over related reduced-order systems. Utilising the behavioural framework, we extend upon the standard hierarchical control refinement for ordinary systems and allow for algebraic couplings inherent to descriptor systems.Comment: 8 pages, 3 figure

Coalgebra, concurrency and control

Coalgebra is used to generalize notions and techniques from concurrency theory, in order to apply them to problems concerning the supervisory control of discrete event systems. The main ingredients of this approach are the characterization of controllability in terms of (a variant of) the notion of bisimulation, and the observation that the fa

Models as arrows: the role of dialgebras

A large number of computational processes can suitably be described as a combination of construction, i.e. algebraic, and observation, i.e. coalgebraic, structures. This paper suggests dialgebras as a generic model in which such structures can be combined and proposes a small calculus of dialgebras including a wrapping combinator and se- quential composition. To take good care of invariants in software design, the paper also discusses how dialgebras can be typed by predicates and proves that invariants are preserved through composition. This lays the foundations for a full calculus of invariant proof-obligation discharge for dialgebraic models.Fundação para a Ciência e a Tecnologia (FCT

Formální komponentový model pro mobilní architektury

Disertační práce se zabývá modelováním komponentových systémů a formálním popisem jejich chování. Řešení je založeno na vlastním komponentovém modelu, který je popsán meta-modelem, z logického pohledu, a popisem v pi-kalkulu, z procesního pohledu. Je ukázáno, že komponentový model pokrývá dynamické aspekty softwarových architektur včetně mobility jejich komponent. Dále je popsán způsob modelování chování v architekturách orientovaných na služby a přechod ke komponentovým systémům. Chování konkrétní architektury orientované na služby lze pak vyjádřit jako jediný proces v pi-kalkulu. V závěru práce je navržené řešení ověřeno na případové studii prostředí pro testování kritických aplikací. Přínosem disertační práce je zejména zmíněná podpora dynamických architektur a integrace s architekturami orientovanými na služby.In the thesis, we propose an approach to modelling of component-based systems and formal description of their behaviour. The approach is based on a novel component model defined by a metamodel in a logical view and by description in the pi-calculus in a process view. We show that the component model addresses the dynamic aspects of software architectures including the component mobility. Furthermore, we propose a method of behavioural modelling of service-oriented architectures to pass smoothly from service level to component level and to describe behaviour of a whole system, services and components, as a single pi-calculus process. Finally, we illustrate an application of our approach on a case study of an environment for functional testing of complex safety-critical systems. The support of dynamic architecture and the integration with service-oriented architecture compromise the main advantages of our approach.Katedra softwarového inženýrstvíDepartment of Software EngineeringFaculty of Mathematics and PhysicsMatematicko-fyzikální fakult

Software engineering : redundancy is key

Software engineers are humans and so they make lots of mistakes. Typically 1 out of 10 to 100 tasks go wrong. The only way to avoid these mistakes is to introduce redundancy in the software engineering process. This article is a plea to consciously introduce several levels of redundancy for each programming task. Depending on the required level of correctness, expressed in a residual error probability (typically 10-3 to 10-10), each programming task must be carried out redundantly 4 to 8 times. This number is hardly influenced by the size of a programming endeavour. Training software engineers does have some effect as non trained software engineers require a double amount of redundant tasks to deliver software of a desired quality. More compact programming, for instance by using domain specific languages, only reduces the number of redundant tasks by a small constant