Architectures in parametric component-based systems: Qualitative and quantitative modelling

One of the key aspects in component-based design is specifying the software architecture that characterizes the topology and the permissible interactions of the components of a system. To achieve well-founded design there is need to address both the qualitative and non-functional aspects of architectures. In this paper we study the qualitative and quantitative formal modelling of architectures applied on parametric component-based systems, that consist of an unknown number of instances of each component. Specifically, we introduce an extended propositional interaction logic and investigate its first-order level which serves as a formal language for the interactions of parametric systems. Our logics achieve to encode the execution order of interactions, which is a main feature in several important architectures, as well as to model recursive interactions. Moreover, we prove the decidability of equivalence, satisfiability, and validity of first-order extended interaction logic formulas, and provide several examples of formulas describing well-known architectures. We show the robustness of our theory by effectively extending our results for parametric weighted architectures. For this, we study the weighted counterparts of our logics over a commutative semiring, and we apply them for modelling the quantitative aspects of concrete architectures. Finally, we prove that the equivalence problem of weighted first-order extended interaction logic formulas is decidable in a large class of semirings, namely the class (of subsemirings) of skew fields.Comment: 53 pages, 11 figure

Contributions to multi-view modeling and the multi-view consistency problem for infinitary languages and discrete systems

The modeling of most large and complex systems, such as embedded, cyber-physical, or distributed systems, necessarily involves many designers. The multiple stakeholders carry their own perspectives of the system under development in order to meet a variety of objectives, and hence they derive their own models for the same system. This practice is known as multiview modeling, where the distinct models of a system are called views. Inevitably, the separate views are related, and possible overlaps may give rise to inconsistencies. Checking for multiview consistency is key to multi-view modeling approaches, especially when a global model for the system is absent, and can only be synthesized from the views. The present thesis provides an overview of the representative related work in multi-view modeling, and contributes to the formal study of multi-view modeling and the multi-view consistency problem for views and systems described as sets of behaviors. In particular, two distinct settings are investigated, namely, infinitary languages, and discrete systems. In the former research, a system and its views are described by mixed automata, which accept both finite and infinite words, and the corresponding infinitary languages. The views are obtained from the system by projections of an alphabet of events (system domain) onto a subalphabet (view domain), while inverse projections are used in the other direction. A systematic study is provided for mixed automata, and their languages are proved to be closed under union, intersection, complementation, projection, and inverse projection. In the sequel, these results are used in order to solve the multi-view consistency problem in the infinitary language setting. The second research introduces the notion of periodic sampling abstraction functions, and investigates the multi-view consistency problem for symbolic discrete systems with respect to these functions. Apart from periodic samplings, inverse periodic samplings are also introduced, and the closure of discrete systems under these operations is investigated. Then, three variations of the multi-view consistency problem are considered, and their relations are discussed. Moreover, an algorithm is provided for detecting view inconsistencies. The algorithm is sound but it may fail to detect all inconsistencies, as it relies on a state-based reachability, and inconsistencies may also involve the transition structure of the system

Weighted recognizability over infinite alphabets

We introduce weighted variable automata over infinite alphabets and commutative semirings. We prove that the class of their behaviors is closed under sum, and under scalar, Hadamard, Cauchy, and shuffle products, as well as star operation. Furthermore, we consider rational series over infinite alphabets and we state a Kleene-Schützenberger theorem. We introduce a weighted monadic second order logic and a weighted linear dynamic logic over infinite alphabets and investigate their relation to weighted variable automata. An application of our theory, to series over the Boolean semiring, concludes to new results for the class of languages accepted by variable automata

A formal algebraic approach for the quantitative modeling of connectors in architectures

In this paper we propose an algebraic formalization of connectors in the quantitative setting in order to address the performance issues related with the architectures of component-based systems. For this, we firstly introduce a weighted Algebra of Interactions over a set of ports and a commutative and idempotent semiring. The algebra serves sufficiently for modeling well-known coordination schemes in the weighted setup. In turn, we introduce and study a weighted Algebra of Connectors over a set of ports and a commutative and idempotent semiring, which extends the weighted Algebra of Interactions with types that express two different modes of synchronization, in particular, Rendezvous and Broadcast. Moreover, we show the expressiveness of the algebra by modeling several weighted connectors. Finally, we introduce a congruence relation for weighted connectors and provide conditions for proving congruence between distinct weighted connectors.Comment: 58 pages, 5 figure