Behavioural protocol representation and adaptation in a service composition framework

Service Oriented Architecture (SOA) is a paradigm for building software applications from loosely-coupled services. Building large applications often involves combining services into bigger ones. This process is known as service composition. In the dynamic, open and distributed environments of SOA, services are not always available and new services are introduced that might provide other characteristics that are more beneficial to the current system than the existing ones. In order to utilise different services, a service composition framework needs to allow its constituent services to be substituted and ensure that the services involved in the composition interact with each other in a compatible manner both in terms of functionality and sequence of exchanged messages (or behavioural protocol). In this thesis, we propose a service composition framework that has three capabilities: (i) specifying behavioural protocols among services and offering support for behavioural protocols including: aggregation of protocols, consistency checking and run-time protocol monitoring, (ii) checking compatibilities of potential services, and (iii) proposing adaptor patterns to alleviate the potential incompatibilities between services and the specified required sequence of interactions. Our service composition framework is built based on the Role Oriented Adaptive Design (ROAD) framework. Required sequences of interactions are defined by using a declarative pattern-based specification, the Interaction Rule Specification (IRS). The compatibilities of services are checked by a mechanism involving three steps: converting IRS descriptions to Finite State Automata (FSAs), converting services’ behavioural specifications (e.g. in OWL-S) to FSAs, and finally analysing the resulting FSAs to indentify compatibilities of potential services. In the case that services are incompatible to the required sequence of interactions, we propose three adaptation patterns that can be used to alleviate mismatches. The run-time overheads of behavioural protocol’s conversion to FSA and analysis are also evaluated. By supporting automated checking of behavioural compatibilities between services and providing adaptor patterns to address the identified behavioural mismatches, this thesis presents a further step towards automated service composition.