Tau Be or not Tau Be? - A Perspective on Service Compatibility and Substitutability

One of the main open research issues in Service Oriented Computing is to propose automated techniques to analyse service interfaces. A first problem, called compatibility, aims at determining whether a set of services (two in this paper) can be composed together and interact with each other as expected. Another related problem is to check the substitutability of one service with another. These problems are especially difficult when behavioural descriptions (i.e., message calls and their ordering) are taken into account in service interfaces. Interfaces should capture as faithfully as possible the service behaviour to make their automated analysis possible while not exhibiting implementation details. In this position paper, we choose Labelled Transition Systems to specify the behavioural part of service interfaces. In particular, we show that internal behaviours (tau transitions) are necessary in these transition systems in order to detect subtle errors that may occur when composing a set of services together. We also show that tau transitions should be handled differently in the compatibility and substitutability problem: the former problem requires to check if the compatibility is preserved every time a tau transition is traversed in one interface, whereas the latter requires a precise analysis of tau branchings in order to make the substitution preserve the properties (e.g., a compatibility notion) which were ensured before replacement.Comment: In Proceedings WCSI 2010, arXiv:1010.233

Folk theorems on the correspondence between state-based and event-based systems

Kripke Structures and Labelled Transition Systems are the two most prominent semantic models used in concurrency theory. Both models are commonly believed to be equi-expressive. One can find many ad-hoc embeddings of one of these models into the other. We build upon the seminal work of De Nicola and Vaandrager that firmly established the correspondence between stuttering equivalence in Kripke Structures and divergence-sensitive branching bisimulation in Labelled Transition Systems. We show that their embeddings can also be used for a range of other equivalences of interest, such as strong bisimilarity, simulation equivalence, and trace equivalence. Furthermore, we extend the results by De Nicola and Vaandrager by showing that there are additional translations that allow one to use minimisation techniques in one semantic domain to obtain minimal representatives in the other semantic domain for these equivalences

Transactional Reduction of Component Compositions

Abstract. Behavioural protocols are beneficial to Component-Based Software Engineering and Service-Oriented Computing as they foster automatic procedures for discovery, composition, composition correctness checking and adaptation. However, resulting composition models (e.g., orchestrations or adaptors) often contain redundant or useless parts yielding the state explosion problem. Mechanisms to reduce the state space of behavioural composition models are therefore required. While reduction techniques are numerous, e.g., in the process algebraic framework, none is suited to compositions where provided/required services correspond to transactions of lower-level individual event based communications. In this article we address this issue through the definition of a dedicated model and reduction techniques. They support transactions and are therefore applicable to service architectures.

A pilot study on the feasibility of European harmonized Human Biomonitoring : strategies towards a common approach, challenges and opportunities

© 2014 Elsevier Inc. All rights reserved.In 2004 the European Commission and Member States initiated activities towards a harmonized approach for Human Biomonitoring surveys throughout Europe. The main bjective was to sustain environmental health policy by building a coherent and sustainable framework and by increasing the comparability of data across countries. A pilot study to test common guidelines for setting up surveys was considered a key step in this process. Through a bottom-up approach that included all stakeholders, a joint study protocol was elaborated. From September 2011 till February 2012, 17 European countries collected data from 1844 mother–child pairs in the frame of DEMOnstration of a study to COordinate and Perform Human Biomonitoring on a European Scale (DEMOCOPHES).1 Mercury in hair and urinary cadmium and cotinine were selected as biomarkers of exposure covered by sufficient analytical experience. Phthalate metabolites and Bisphenol A in urine were added to take into account increasing public and political awareness for emerging types of contaminants and to test less advanced markers/markers covered by less analytical experience. Extensive efforts towards chemo-analytical comparability were included. The pilot study showed that common approaches can be found in a context of considerable differences with respect to experience and expertize, socio-cultural background, economic situation and national priorities. It also evidenced that comparable Human Biomonitoring results can be obtained in such context. A European network was built, exchanging information, expertize and experiences, and providing training on all aspects of a survey. A key challenge was finding the right balance between a rigid structure allowing maximal comparability and a flexible approach increasing feasibility and capacity building. Next steps in European harmonization in Human Biomonitoring surveys include the establishment of a joint process for prioritization of substances to cover and biomarkers to develop, linking biomonitoring surveys with health examination surveys and with research, and coping with the diverse implementations of EU regulations and international guidelines with respect to ethics and privacy.Financial support: COPHES (COnsortium to Perform Human Biomonitoring on a European Scale) was funded by the Seventh EU Framework Programme 2007–2011 under grant agreement no [244237]. DEMOCOPHES (DEMOnstration of a study to COordinate and Perform Human Biomonitoring on a European Scale) was co-funded (50%:50%) by the European Commission LIFE+ Programme (LIFE09/ENV/BE/000410) and the partners