We envisage tomorrow's services to become increasingly pervasive, being deployed within buildings, transport systems, markets, as well as people portable devices. Such services will be, by their own nature, simple and fine grained; as a consequence, service composition will become crucial to deliver rich functionalities that satisfy end users' requests. The higher the dynamic nature of the environment, the higher the chances that services will move out-of-reach before the composition completes, causing the service as a whole to fail. We argue that, in order to enable the successful provision of compound services in mobile environments, the reliability of the composition must be measured and reasoned about. In this paper, we present MoSCA, a middleware that facilitates the rapid development and deployment of reliable composite services. At design-time, a MoSCA Service is uniquely identified within an OWL-S ontology, and described as a composition of further MoSCA Services, which can themselves be composite or basic. At run-time, whenever a (composite) service is invoked, MoSCA selects the providers, among those currently available, that are capable of collectively delivering the (composite) service with the highest reliability. Reliability is estimated by reasoning about providers' historical colocation patterns, that are learned over time. Unforeseen changes to such patterns are being monitored as well, potentially triggering re-bindings during service execution. Copyright 2008 ACM.
['L Del Prete', 'Licia Capra']
MoSCA: Seamless execution of mobile composite services