A Note on the Expressiveness of BIP

We extend our previous algebraic formalisation of the notion of component-based framework in order to formally define two forms, strong and weak, of the notion of full expressiveness. Our earlier result shows that the BIP (Behaviour-Interaction-Priority) framework does not possess the strong full expressiveness. In this paper, we show that BIP has the weak form of this notion and provide results detailing weak and strong full expressiveness for classical BIP and several modifications, obtained by relaxing the constraints imposed on priority models.Comment: In Proceedings EXPRESS/SOS 2016, arXiv:1608.0269

Sequential Composition in the Presence of Intermediate Termination (Extended Abstract)

The standard operational semantics of the sequential composition operator gives rise to unbounded branching and forgetfulness when transparent process expressions are put in sequence. Due to transparency, the correspondence between context-free and pushdown processes fails modulo bisimilarity, and it is not clear how to specify an always terminating half counter. We propose a revised operational semantics for the sequential composition operator in the context of intermediate termination. With the revised operational semantics, we eliminate transparency, allowing us to establish a close correspondence between context-free processes and pushdown processes. Moreover, we prove the reactive Turing powerfulness of TCP with iteration and nesting with the revised operational semantics for sequential composition.Comment: In Proceedings EXPRESS/SOS 2017, arXiv:1709.00049. arXiv admin note: substantial text overlap with arXiv:1706.0840

On the Executability of Interactive Computation

The model of interactive Turing machines (ITMs) has been proposed to characterise which stream translations are interactively computable; the model of reactive Turing machines (RTMs) has been proposed to characterise which behaviours are reactively executable. In this article we provide a comparison of the two models. We show, on the one hand, that the behaviour exhibited by ITMs is reactively executable, and, on the other hand, that the stream translations naturally associated with RTMs are interactively computable. We conclude from these results that the theory of reactive executability subsumes the theory of interactive computability. Inspired by the existing model of ITMs with advice, which provides a model of evolving computation, we also consider RTMs with advice and we establish that a facility of advice considerably upgrades the behavioural expressiveness of RTMs: every countable transition system can be simulated by some RTM with advice up to a fine notion of behavioural equivalence.Comment: 15 pages, 0 figure

Design and Optimisation of the FlyFast Front-end for Attribute-based Coordination

Collective Adaptive Systems (CAS) consist of a large number of interacting objects. The design of such systems requires scalable analysis tools and methods, which have necessarily to rely on some form of approximation of the system's actual behaviour. Promising techniques are those based on mean-field approximation. The FlyFast model-checker uses an on-the-fly algorithm for bounded PCTL model-checking of selected individual(s) in the context of very large populations whose global behaviour is approximated using deterministic limit mean-field techniques. Recently, a front-end for FlyFast has been proposed which provides a modelling language, PiFF in the sequel, for the Predicate-based Interaction for FlyFast. In this paper we present details of PiFF design and an approach to state-space reduction based on probabilistic bisimulation for inhomogeneous DTMCs.Comment: In Proceedings QAPL 2017, arXiv:1707.0366

Sequential Composition in the Presence of Intermediate Termination (Extended Abstract)

The standard operational semantics of the sequential composition operator gives rise to unbounded branching and forgetfulness when transparent process expressions are put in sequence. Due to transparency, the correspondence between context-free and pushdown processes fails modulo bisimilarity, and it is not clear how to specify an always terminating half counter. We propose a revised operational semantics for the sequential composition operator in the context of intermediate termination. With the revised operational semantics, we eliminate transparency, allowing us to establish a close correspondence between context-free processes and pushdown processes. Moreover,we prove the reactive Turing powerfulness of TCP with iteration and nesting with the revised operational semantics for sequential composition

Proposition des modèles et de processus structurés pour le développement d’environnements collaboratifs synchrones : application aux réunions de revue de conception

Development of collaborative environment is a complex process. The complexity lies in the fact that collaborative environment development involves a lot of decision making. Several tradeoffs need to be made to satisfy current and future requirements from a potentially various set of user profiles. The handling of these complexities poses challenges for researcher, developers and companies. The knowledge required to make suitable design decisions and to rigorously evaluate those design decisions is usually broad, complex, and evolving. In Part-I of this thesis we investigate to formulate the general knowledge about: synchronous collaborative work which conceptualize the problem domain, synchronous collaborative environment which conceptualize the solution domain and synchronous collaborative environment evaluation which conceptualize the evaluation of whole or part of the proposed solution for the specified problem. This formulation has been done through literature study and leaded to the Concept Maps. The results generate three models: SyCoW (synchronous collaborative work), SyCoE (synchronous collaborative environment) and SyCoEE (synchronous collaborative environment evaluation). In Part-II of this thesis we proposed a process for selection/development of collaborative environment, where we demonstrate how SyCoW, SyCoE and SyCoEE support this process in different ways. Through the proposed process we present the development of new synchronous collaborative environment for design review meeting, named, MT-DT. MT-DT has been designed, developed and evaluated by the author in her PhD. MT-DT consist of a multi-touch table with specific 3D software application which support collaborative design review activities. The results of evaluation confirmed the usability of MT-DT and provide arguments for our choices which we made during development of MT-DT.Le développement d'un environnement collaboratif est un processus complexe. La complexité réside dans le fait que ce développement implique beaucoup de prise de décisions. De multiples compromis doivent être faits pour répondre aux exigences actuelles et futures d'utilisateurs aux profils variés. La prise en compte de cette complexité pose des problèmes aux chercheurs, développeurs et utilisateurs. Les informations et données requises pour prendre des décisions adéquates de conception et évaluer rigoureusement ces décisions sont nombreuses, parfois indéterminées et en constante évolution. Dans la partie-I de cette thèse, nous formulons les connaissances générales sur le travail collaboratif synchrone qui constituent l'état de l'art du domaine du problème. Nous pratiquons de même pour les environnements collaboratifs synchrones (domaine de la solution technique) et leur cette formulation s'appuie sur une étude de la littérature et conduit à la proposition de Schéma Conceptuel (Concept Maps). Nous en déduisons trois modèles: SyCoW (travail collaboratif synchrone), SyCoE (environnement collaboratif synchrone) et SyCoEE (évaluation environnement collaboratif synchrone). Dans la partie II de cette thèse, nous proposons un processus pour la sélection / développement d'un environnement collaboratif, où nous démontrons comment les modèles SyCoW, SyCoE et SyCoEE structurent ce processus. Grâce à la mise en œuvre de la démarche proposée, nous présentons le développement d'un nouvel environnement collaboratif synchrone pour une réunion de revue de conception nommé MT-DT. MT-DT a été conçu, développé et évalué par l'auteur dans sa thèse de doctorat. MT-DT est une application logicielle 3D spécifique à une table multi-touche qui assiste les activités de revue de conception collaborative. Les résultats de l'évaluation ont confirmé la convivialité de MT-DT et fournissent des éléments de validation des choix que nous avons faits au cours du développement de MT-DT

Computer Aided Verification

The open access two-volume set LNCS 11561 and 11562 constitutes the refereed proceedings of the 31st International Conference on Computer Aided Verification, CAV 2019, held in New York City, USA, in July 2019. The 52 full papers presented together with 13 tool papers and 2 case studies, were carefully reviewed and selected from 258 submissions. The papers were organized in the following topical sections: Part I: automata and timed systems; security and hyperproperties; synthesis; model checking; cyber-physical systems and machine learning; probabilistic systems, runtime techniques; dynamical, hybrid, and reactive systems; Part II: logics, decision procedures; and solvers; numerical programs; verification; distributed systems and networks; verification and invariants; and concurrency

Specification and Verification of Contract-Based Applications

Nowadays emerging paradigms are being adopted by several companies, where applications are built by assembling loosely-coupled distributed components, called services. Services may belong to possibly mutual distrusted organizations and may have conflicting goals. New methodologies for designing and verifying these applications are necessary for coping with new scenarios in which a service does not adhere with its prescribed behaviour, namely its contract. The thesis tackles this problem by proposing techniques for specifying and verifying distributed applications. The first contribution is an automata-based model checking technique for ensuring both service compliance and security requirements in a composition of services. We further develop the automata-based approach by proposing a novel formal model of contracts based on tailored finite state automata, called contract automata. The proposed model features several notions of contract agreement described from a language-theoretic perspective, for characterising the modalities in which the duties and requirements of services are fulfilled. Contract automata are equipped with different composition operators, to uniformly model both single and composite services, and techniques for synthesising an orchestrator to enforce the properties of agreement. Algorithms for verifying these properties are introduced, based on control theory and linear programming techniques. The formalism assumes the existence of possible malicious components trying to break the overall agreement, and techniques for detecting and banning eventually liable services are described. We study the conditions for dismissing the central orchestrator in order to generate a distributed choreography of services, analysing both closed and open choreographed systems, with synchronous or asynchronous interactions. We relate contract automata with different intutionistic logics for contracts, introduced for solving mutual circular dependencies between the requirements and the obligations of the parties, with either linear or non-linear availability of resources. Finally, a prototypical tool implementing the theory developed in the thesis is presented

Políticas de Copyright de Publicações Científicas em Repositórios Institucionais: O Caso do INESC TEC

A progressiva transformação das práticas científicas, impulsionada pelo desenvolvimento das novas Tecnologias de Informação e Comunicação (TIC), têm possibilitado aumentar o acesso à informação, caminhando gradualmente para uma abertura do ciclo de pesquisa. Isto permitirá resolver a longo prazo uma adversidade que se tem colocado aos investigadores, que passa pela existência de barreiras que limitam as condições de acesso, sejam estas geográficas ou financeiras. Apesar da produção científica ser dominada, maioritariamente, por grandes editoras comerciais, estando sujeita às regras por estas impostas, o Movimento do Acesso Aberto cuja primeira declaração pública, a Declaração de Budapeste (BOAI), é de 2002, vem propor alterações significativas que beneficiam os autores e os leitores. Este Movimento vem a ganhar importância em Portugal desde 2003, com a constituição do primeiro repositório institucional a nível nacional. Os repositórios institucionais surgiram como uma ferramenta de divulgação da produção científica de uma instituição, com o intuito de permitir abrir aos resultados da investigação, quer antes da publicação e do próprio processo de arbitragem (preprint), quer depois (postprint), e, consequentemente, aumentar a visibilidade do trabalho desenvolvido por um investigador e a respetiva instituição. O estudo apresentado, que passou por uma análise das políticas de copyright das publicações científicas mais relevantes do INESC TEC, permitiu não só perceber que as editoras adotam cada vez mais políticas que possibilitam o auto-arquivo das publicações em repositórios institucionais, como também que existe todo um trabalho de sensibilização a percorrer, não só para os investigadores, como para a instituição e toda a sociedade. A produção de um conjunto de recomendações, que passam pela implementação de uma política institucional que incentive o auto-arquivo das publicações desenvolvidas no âmbito institucional no repositório, serve como mote para uma maior valorização da produção científica do INESC TEC.The progressive transformation of scientific practices, driven by the development of new Information and Communication Technologies (ICT), which made it possible to increase access to information, gradually moving towards an opening of the research cycle. This opening makes it possible to resolve, in the long term, the adversity that has been placed on researchers, which involves the existence of barriers that limit access conditions, whether geographical or financial. Although large commercial publishers predominantly dominate scientific production and subject it to the rules imposed by them, the Open Access movement whose first public declaration, the Budapest Declaration (BOAI), was in 2002, proposes significant changes that benefit the authors and the readers. This Movement has gained importance in Portugal since 2003, with the constitution of the first institutional repository at the national level. Institutional repositories have emerged as a tool for disseminating the scientific production of an institution to open the results of the research, both before publication and the preprint process and postprint, increase the visibility of work done by an investigator and his or her institution. The present study, which underwent an analysis of the copyright policies of INESC TEC most relevant scientific publications, allowed not only to realize that publishers are increasingly adopting policies that make it possible to self-archive publications in institutional repositories, all the work of raising awareness, not only for researchers but also for the institution and the whole society. The production of a set of recommendations, which go through the implementation of an institutional policy that encourages the self-archiving of the publications developed in the institutional scope in the repository, serves as a motto for a greater appreciation of the scientific production of INESC TEC