Reliable Discovery and Selection of Composite Services in Mobile Environments

Abstract

Service providers as we know them nowadays are the always-on "static" web service providers, that aim at Five9 availability (99.999%). Formal, or de-facto, standards, such as WSDL and BPEL, have become technology enablers for the easy discovery, use and coordination of such services. However, 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. Composing services in mobile environments opens up significant challenges. In particular, the Five9 availability assumption no longer holds: 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 completion of compound services, the reliability of the composition must be measured and reasoned about. In order to do so, we propose to dynamically deploy a prediction model to estimate the duration of colocation between component services. These estimates are fed in input to a service composition semantics reasoner, which then autonomically selects those providers, within the current environment, that maximise the chances of successful compound service completion. We demonstrate the positive impact that the reliability reasoning has onto the ratio of successfully completed compound services in a typical human movement scenario.

Choreography-based vs orchestration-based service composition in opportunistic networks

“…In practice, adhoc networks supporting pervasive environments are usually intermittently-connected networks, and therefore opportunistic or delay-tolerant networking techniques must be used to improve communication in such networks. In [8], Capra et al present a service composition framework for mobile environments that allows to improve the service composition reliability by considering the mobility pattern of devices and their colocation duration (the probability of service access is related to the colocation duration). Similarly, work in [9] tries to improve service composition dependability by characterizing the service providers' mobility and by tolerating an uncertain mobility of these ones.…”

Opportunistic service composition in pervasive networks

“…Like research works [3], [4], [5], [7], and [8], it supports an incremental and partial composition mechanism, thus allowing to compose services progressively according to their discovery, and to avoid to rebuild the whole composition when a service provider involved in the composition process becomes unreachable. In order to cope with connection disruptions in the service discovery and invocation processes, our system leverages on the C3PO opportunistic computing middleware, dedicated to the development and the deployment of opportunistic Android applications in the context of spontaneous and ephemeral social networks [9].…”

Towards User-Oriented Application Composition

“…Thus, the allocation algorithm will be able to evaluate different application compositions according to their reliability. The predictor can be designed, as suggested by Del Prete and Carpa [8].…”

“…in wireless networks). Besides, the affinity constraints enable reliable application composition like in the prototype developed by Del Prete et al [8]. To achieve this, our platform model has to have additional properties specifying reliability of each network node.…”