Verification of Web Service Descriptions using Graph-based Traversal Algorithms

Service discovery and composition techniques require a careful and accurate specification of the functional and behavioural descriptions of services. Otherwise, the located services may not provide the requested functionality and composite services may incorporate services that are incompatible and uncomposable. This paper proposes two formalisms for accurately specifying functional and behavioural descriptions and a technique for detecting errors in the specifications. Unlike existing frameworks, functional descriptions created with the proposed formalism enable the purpose of a service, and the data transformations and state transitions performed by it to be modelled together. The behavioural description formalism is capable of accurately representing the effects of interactions and the temporal relationships between them. The technique is developed by extending a pre-order depth-first search algorithm, which traverses through the interaction protocol of a service and determines whether the valid terminal state of the service can be derived from its initial state. A sample case study in which we detect errors in the functional and behavioural descriptions of a service by verifying them using the proposed technique is provided.