COWS

Cette opération QSL commune à CASSIS et ECOO vise à étudier l'utilisation du raisonnement par contraintes pour la conception sûre de services Web. Nos objectifs sont multiples. Un premier objectif est de spécifier formellement la composition de services Web. Un deuxième concerne la coordination d'un ensemble de services, en garantissant que l'exécution est sûre, tout en étant conforme à ce qui est attendu par toutes les parties. Enfin, un troisième objectif concerne les mécanismes permettant de surveiller la manière dont une composition précédemment spécifiée s'exécute, et de savoir réagir lorsque survient une exception. Il est clair que les objectifs sont étroitement liés, et que nous visons la définition d'un modèle permettant de composer, de coordonner, et de surveiller.

Nous organisons une journée autour du thème de COWS le 27 juin 2006. L'objectif est d'avoir des échanges de points de vue en ce qui concerne la composition de services Web. Le programme de la journée est le suivant:

9h45	Opening of the workshop
10h-11h15	Farouk Toumani (LIMOS, Clermont-Ferrand), Flexible Techniques for Analysing and Managing Web Service Protocols In the area of Web services and service-oriented architectures, business protocols are rapidly gaining importance and mindshare as a necessary part of Web service descriptions. Their immediate benefit is that they provide developers with information on how to write clients that can correctly interact with a given service or with a set of services. This talk deals with the design of a model for representing web service protocols and implementation of techniques for, analyzing and managing such protocols. It discusses the different ways in which the middleware can leverage protocol descriptions, and focuses in particular on the notions of protocol compatibility, equivalence, and replaceability. They characterise whether two services can interact based on their protocol definition, whether a service can replace another in general or when interacting with specific clients, and which are the set of possible interactions among two services. This research is carried out in the context of ServiceMosaic (http://servicemosaic.isima.fr/), a joint project which aims at developing a model-driven framework for web service lifecycle management. Download the presentation in PDF (630 Ko).
11h15-12h30	Dirk Beyer (EPFL, Switzerland), Web Service Interfaces We present a language for specifying web service interfaces. A web service interface puts three kinds of constraints on the users of the service. First, the interface specifies the methods that can be called by a client, together with types of input and output parameters; these are called signature constraints. Second, the interface may specify propositional constraints on method calls and output values that may occur in a web service conversation; these are called consistency constraints. Third, the interface may specify temporal constraints on the ordering of method calls; these are called protocol constraints. The interfaces can be used to check, first, if two or more web services are compatible, and second, if a web service A can be safely substituted for a web service B. The algorithm for compatibility checking verifies that two or more interfaces fulfill each others' constraints. The algorithm for substitutivity checking verifies that service A demands fewer and fulfills more constraints than service B. Download the presentation in PDF (520 Ko).
12h30-14h00	Lunch
14h00-15h15	Raman Kazhamiakin (Trento, Italy), Verification and Validation of Web Service Compositions We present a formal framework for modelling, verification and validation of Web service compositions defined as a set of interacting business processes. The key features of this framework are (i) the ability to model and analyze various asynchronous communication models and their impact on the behavior of the composition; (ii) the possibility to take into account data flow of the compositions; and (iii) the set of techniques to represent, verify, and compute time-related properties of the composite system. We also discuss a set of algorithms and techniques adopted for these purposes. In particular, we present a problem of finding a communication model that better describes the given scenario (adequacy problem), an abstraction-based approach for the design and analysis of the data flow in service compositions, and the techniques based on the duration calculi that allow to perform qualitative and quantitative analysis of timed properties of the distributed compositions. Download the presentation in PDF (1600 Ko).
15h15-16h00	Fahima Cheikh (IRIT, Toulouse), Computational Analyses of Interacting Web Services: a Logical Approach The problem of combining services, also named composition problem, has been investigated since the 2000's with many solutions proposed to compose services together, is to interleave their actions sequences in accordance with a client specification. In this talk, I will present a new model where services are able to execute actions, to send messages and to receive messages. The model I will present is a variant of the model proposed by D. Berardi and al. Then, I will define for this model the composition problem and I will give theoretical results about its complexity. Finally, I will talk about interesting future works concerning the integration of security issues into web services. Download the presentation in PDF (250 Ko).
16h	Conclusion