Meta SOS - A Maude Based SOS Meta-Theory Framework

Meta SOS is a software framework designed to integrate the results from the meta-theory of structural operational semantics (SOS). These results include deriving semantic properties of language constructs just by syntactically analyzing their rule-based definition, as well as automatically deriving sound and ground-complete axiomatizations for languages, when considering a notion of behavioural equivalence. This paper describes the Meta SOS framework by blending aspects from the meta-theory of SOS, details on their implementation in Maude, and running examples.Comment: In Proceedings EXPRESS/SOS 2013, arXiv:1307.690

A Notion of Glue Expressiveness for Component-Based Systems

Comparison between different formalisms and models is often by flattening structure and reducing them to behaviourally equivalent models e.g. automaton and Turing machine. This leads to a notion of expressiveness which is not adequate for component-based systems where separation between behaviour and coordination mechanisms is essential. The paper proposes a notion of glue expressiveness for component-based frameworks characterizing their ability to coordinate components. Glue is a closed under composition set of operators mapping tuples of behaviour into behaviour. Glue operators preserve behavioural equivalence. They only restrict the behaviour of their arguments by performing memoryless coordination. Behavioural equivalence induces an equivalence on glue operators. We compare expressiveness of two glues G1 and G2 by considering whether glue operators of G1 have equivalent ones in G2 (strong expressiveness). Weak expressiveness is defined by allowing a finite number of additional behaviours in the arguments of operators of G2. We propose an SOS-style definition of glues, where operators are characterized as sets of SOS-rules specifying the transition relation of composite components from the transition relations of their constituents. We provide expressiveness results for the glues of BIP and of process algebras such as CCS, CSP and SCCS. We show that for the considered expressiveness criteria, glues of the considered process calculi are less expressive than general SOS glue. Furthermore, glue of BIP has exactly the same strong expressiveness as glue definable by the SOS characterization

Contextual behavioural Metrics (Extended Version)

We introduce contextual behavioural metrics (CBMs) as a novel way of measuring the discrepancy in behaviour between processes, taking into account both quantitative aspects and contextual information. This way, process distances by construction take the environment into account: two (non-equivalent) processes may still exhibit very similar behaviour in some contexts, e.g., when certain actions are never performed. We first show how CBMs capture many well-known notions of equivalence and metric, including Larsen's environmental parametrized bisimulation. We then study compositional properties of CBMs with respect to some common process algebraic operators, namely prefixing, restriction, non-deterministic sum, parallel composition and replication.Comment: Extended version of a paper accepted for publication in proc. CONCUR 202

A Semantic Framework for Architecture Modelling

Architectures are common means for organising coordination between components in order to build complex systems and to make them manageable. They allow thinking on a higher plane and avoiding low-level mistakes. Architectures provide means for ensuring correctness-by-construction by enforcing global properties characterising the coordination between components. In this work, we consider the following questions of architecture modelling: 1) how to model architectures; 2) how to compose them if several properties enforced by different architectures are required; 3) how to specify architectures styles that generalise the notion of architectures and represent families of architectures satisfying the same property. An architecture can be considered as an operator that, applied to a set of components, builds a composite component meeting a characteristic property. The underlying concepts of components and their interaction originate from the BIP framework. This thesis is structured in two parts. In the first part, we study the expressiveness of glue operators in the BIP framework. We provide results for classical BIP glue and for several modifications obtained by relaxing the constraints imposed on priority models. We also study an alternative semantics of BIP glue based on the offer predicate. It meets fundamental properties required from component-based frameworks, namely compositionality, incrementality, flattening and modularity. We provide the comparison with the classical BIP semantics and the algorithm for the synthesis of connectors from the interaction logic used to describe coordination constraints. In the second part, we define architectures and propose an architecture composition operator. We study their properties and prove that the composition operator preserves safety properties of its operands. The alternative glue semantics presented in the first part of the thesis allows to extend architectures with priorities. For the specification of architecture styles, we propose configuration logics. We provide a sound and complete axiomatisation of the propositional configuration logic as well as decision procedures for checking that an architecture satisfies a given logical specification. To allow genericity of specifications, we study higher-order extensions of the propositional configuration logic. We illustrate with examples the specification of various architecture styles. We provide an experimental evaluation using the Maude rewriting system to implement the decision procedure for configuration logics. Additionally, we study the relation between the architecture composition operator and the composition of configuration logic formulas