Enabling the ambient intelligence vision means that consumers will be provided with universal and immediate access to available content and services, together with ways of effectively exploiting them. Concentrating on the software system development aspect, this means that the actual implementation of any ambient intelligence application requested by a user can only be resolved at runtime according to the user's specific situation. This paper introduces a base declarative language and associated core middleware, which supports the abstract specification of Ambient Intelligence applications together with their dynamic composition according to the environment. The proposed solution builds on the Web services architecture, whose pervasiveness enables both services availability in most environments, and specification of applications supporting automated retrieval and composition. In addition, dynamic composition of applications is dealt in a way that enforces the quality of service of deployed applications in terms of security and performance.

The Web services architecture is expected to play a prominent role in developing next generation distributed systems. This chapter discusses how to build dependable systems based on the Web services architecture. More specifically, it surveys base fault tolerance mechanisms, considering both backward and forward error recovery mechanisms, and shows how they are adapted to deal with the specifics of the Web in the light of ongoing work in the area. Existing solutions, targeting the development of dependable composite Web services, may be subdivided into two categories that are respectively related to the specification of Web services composition and to the design of dedicated distributed protocols.

No abstract

Abstract. Today's wireless networks and devices support the dynamic composition of mobile distributed systems according to networked services and resources. This has in particular led to the introduction of a number of computing paradigms, among which the Service-Oriented Architecture (SOA) seems to best serve these objectives. However, common SOA solutions restrict considerably the openness of dynamic mobile systems in that they assume a specific middleware infrastructure, over which composed system components have been pre-developed to integrate. On the other hand, the Semantic Web introduces a promising approach towards the integration of heterogeneous components; current semantics-based approaches are, however, restricted to application-level interoperability. Combining the elegant properties of software architecture modeling with the semantic reasoning power of the Semantic Web paradigm, this paper introduces abstract semantic modeling of mobile services that allows both machine reasoning about service composability and enhanced interoperability at both middleware and application level.

This paper proposes a solution based on forward error recovery, oriented towards providing dependability of composite Web services. While exploiting their possible support for fault tolerance (e.g., transactional support at the level of each service), the proposed solution has no impact on the autonomy of the individual Web services, Our solution lies in system structuring in terms of co-operative atomic actions that have a well-defined behaviour, both in the absence and in the presence of service failures. More specifically, we define the notion of Web Service Composition Action (WSCA), based on the Coordinated Atomic Action concept, which allows structuring composite Web services in terms of dependable actions. Fault tolerance can then be obtained as an emergent property of the aggregation of several potentially non-dependable services. We further introduce a framework enabling the development of composite Web services based on WSCAs, consisting of an XML-based language for the specification of WSCAs.

Abstract