Résumé
Ubiquitous computing provides a dynamic access to different functionalities of networkable electronic devices. Whereas basic services have limited use, predefined complex services cannot encompass every end-user's needs nor be adapted to a set of services that are dynamically discovered in an open environment. Alternatively, users need to be provided with means to express their requirements, choosing precisely which services to compose into a scenario of their own. In service-oriented computing, some systems propose mechanisms to develop tailored components that provide composite services; however they are not adapted to end-users, have limited composition capabilities and/or do not consider several characteristics of ubiquitous environments (such as multiple users and devices). This paper presents a novel user-centric system called SaS for mobile personal devices. SaS provides end-users with an easy access to services and a simple GUI to combine them into complex scenarios. A new architectural description language is used to specifically support scenario creation by service composition. Scenario may be shared among users and devices. SaS offers scenario execution control for example to start and stop it but also to query the current state of a scenario. In addition, SaS proposes some mechanisms to maintain scenario availability in case of service/device unavailability. SaS is currently implemented in a proof-of-concept prototype on top of OSGi.