Recent Publications

Pontes R, Maia F, Paulo J, Vilaça R.  2016.  SafeRegions: Performance Evaluation of Multi-party Protocols on HBase. 2016 IEEE 35th Symposium on Reliable Distributed Systems Workshops (SRDSW), 2016 . :31-36.13.pdf
Burihabwa D, Pontes R, Felber P, Maia F, Mercier H, Oliveira R, Paulo J, Schiavoni V.  2016.  On the Cost of Safe Storage for Public Clouds: an Experimental Evaluation.. 35th IEEE International Symposium on Reliable Distributed Systems 2016.. 12.pdf
Kolev B, Bondiombouy C, Valduriez P, Jimenez-Peris R, Pau R, Pereira JO.  2016.  The CloudMdsQL Multistore System. Proceedings of the 2016 International Conference on Management of Data. :2113–2116. Abstract11.pdf

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Kolev B, Bondiombouy C, Levchenko O, Valduriez P, Jimenez-Peris R, Pau R, Pereira JO.  2016.  Design and Implementation of the CloudMdsQL Multistore System. Proceedings of the 6th International Conference on Cloud Computing and Services Science. :352-359. Abstract10.pdf

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Santiago RHN, Bedregal B{\'ı}nRC, Madeira A, Martins MA.  2016.  On Interval Dynamic Logic. Formal Methods: Foundations and Applications - 19th Brazilian Symposium, {SBMF} 2016, Natal, Brazil, November 23-25, 2016, Proceedings. :129–144. Abstract
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Madeira A, Martins MA, Barbosa LS.  2016.  A logic for n-dimensional hierarchical refinement. Proceedings 17th International Workshop on Refinement, Refine@FM 2015, Oslo, Norway, 22nd June 2015. 209:40–56.2.pdf
Madeira A, Barbosa LS, Hennicker R, Martins MA.  2016.  Dynamic Logic with Binders and Its Application to the Development of Reactive Systems. Theoretical Aspects of Computing - ICTAC 2016 - 13th International Colloquium, Taipei, Taiwan, ROC, October 24-31, 2016, Proceedings. 9965:422–440. Abstractmbhm16.pdf

This paper introduces a logic to support the specification and development of reactive systems on various levels of abstraction, from property specifications, concerning e.g. safety and liveness requirements, to constructive specifications representing concrete processes. This is achieved by combining binders of hybrid logic with regular modalities of dynamic logics in the same formalism, which we call D↓-logic. The semantics of our logic focuses on effective processes and is therefore given in terms of reachable transition systems with initial states. The second part of the paper resorts to this logic to frame stepwise development of reactive systems within the software development methodology proposed by Sannella and Tarlecki. In particular, we instantiate the generic concepts of constructor and abstractor implementations by using standard operators on reactive components, like relabelling and parallel composition, as constructors, and bisimulation for abstraction. We also study vertical composition of implementations which relies on the preservation of bisimularity by the constructions on labeleld transition systems.

Neves R, Barbosa LS.  2016.  Hybrid Automata as Coalgebras. Theoretical Aspects of Computing - ICTAC 2016 - 13th International Colloquium, Taipei, Taiwan, ROC, October 24-31, 2016, Proceedings. 9965:385–402. Abstractnb16.pdf

Able to simultaneously encode discrete transitions and continuous behaviour, hybrid automata are the de facto framework for the formal specification and analysis of hybrid systems. The current paper revisits hybrid automata from a coalgebraic point of view. This allows to interpret them as state-based components, and provides a uniform theory to address variability in their definition, as well as the corresponding notions of behaviour, bisimulation, and observational semantics.

Fernandes S, Barbosa LS.  2016.  Applying the 3C Model to FLOSS Communities. Collaboration and Technology - 22nd International Conference, CRIWG 2016, Kanazawa, Japan, September 14-16, 2016, Proceedings. 9848:139–150. Abstractfb16a.pdf

How learning occurs within Free/Libre Open Source (FLOSS) communities and what is the dynamics such projects (e.g. the life cycle of such projects) are very relevant questions when considering the use of FLOSS projects in a formal education setting. This paper introduces an approach based on the 3C collaboration model (communication, coordination and cooperation) to represent the collaborative learning dynamics within FLOSS communities. To explore the collaborative learning potential of FLOSS communities a number of questionnaires and interviews to selected FLOSS contributors were run. From this study a 3C collaborative model applicable to FLOSS communities was designed and discussed.

Veiga L, Janowski T, Barbosa LS.  2016.  Digital Government and Administrative Burden Reduction. Proceedings of the 9th International Conference on Theory and Practice of Electronic Governance, ICEGOV 2016, Montevideo, Uruguay, March 1-3, 2016. :323–326. Abstractvjb16.pdf

Administrative burden represents the costs to businesses, citizens and the administration itself of complying with government regulations and procedures. The burden tends to increase with new forms of public governance that rely less on direct decisions and actions undertaken by traditional government bureaucracies, and more on government creating and regulating the environment for other, non-state actors to jointly address public needs. Based on the reviews of research and policy literature, this paper explores administrative burden as a policy problem, presents how Digital Government (DG) could be applied to address this problem, and identifies societal adoption, organizational readiness and other conditions under which DG can be an effective tool for Administrative Burden Reduction (ABR). Finally, the paper tracks ABR to the latest Contextualization stage in the DG evolution, and discusses possible development approaches and technological potential of pursuing ABR through DG.

Oliveira N, Barbosa LS.  2016.  An Enhanced Model for Stochastic Coordination. Proceedings of the First International Workshop on Formal Methods for and on the Cloud, iFMCloud@IFM 2016, Reykjavik, Iceland, 4th June 2016.. 228:35–45. Abstractob16.pdf

Applications developed over the cloud coordinate several, often anonymous, computational resources, distributed over different execution nodes, within flexible architectures. Coordination models able to represent quantitative data provide a powerful basis for their analysis and validation. This paper extends IMCreo, a semantic model for Stochastic reo based on interactive Markov chains, to enhance its scalability, by regarding each channel and node, as well as interface components, as independent stochastic processes that may (or may not) synchronise with the rest of the coordination circuit.

Silva JMC, Carvalho P, Bispo KA, Lima SR.  2016.  Lightweight Multivariate Sensing in WSNs. Ubiquitous Computing and Ambient Intelligence: 10th International Conference, UCAmI 2016, San Bartolomé de Tirajana, Gran Canaria, Spain, November 29 – December 2, 2016, Part II. :205–211. Abstract

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Pereira R, Couto M, Saraiva J, Cunha J, Fernandes JP.  2016.  The Influence of the Java Collection Framework on Overall Energy Consumption. Proceedings of the 5th International Workshop on Green and Sustainable Software. :15–21. Abstract
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Pereira R, Saraiva J, Cunha J, Fernandes JP.  2016.  User-friendly Spreadsheet Querying: An Empirical Study. Proceedings of the 31st Annual ACM Symposium on Applied Computing. :202–204. Abstract
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Bahsoun JP, Guerraoui R, Shoker A.  2015.  Making BFT Protocols Really Adaptive. In the Proceedings of the 29th IEEE International Parallel & Distributed Processing Symposium. Abstractadapt.pdf

Many state-machine Byzantine Fault Tolerant (BFT) protocols have been introduced so far. Each protocol addressed a different subset of conditions and use-cases. However, if the underlying conditions of a service span different subsets, choosing a single protocol will likely not be a best fit. This yields robustness and performance issues which may be even worse in services that exhibit fluctuating conditions and workloads.
In this paper, we reconcile existing state-machine BFT protocols in a single adaptive BFT system, called ADAPT, aiming at covering a larger set of conditions and use-cases, probably the union of individual subsets of these protocols. At anytime, a launched protocol in ADAPT can be aborted and replaced by another protocol according to a potential change (an event) in the underlying system conditions. The launched protocol is chosen according to an “evaluation process” that takes into consideration both: protocol characteristics and its performance. This is achieved by applying some mathematical formulas that match the profiles of protocols to given user (e.g., service owner) preferences. ADAPT can assess the profiles of protocols (e.g., throughput) at run-time using Machine Learning prediction mechanisms to get accurate evaluations. We compare ADAPT with well known BFT protocols showing that it outperforms others as system conditions change and under dynamic workloads.