A declarative approach to composing web services in dynamic environments

A recent trend in E-business is the deployment of a variety of web services by product and service vendors to facilitate B2B and B2C E-commerce. To utilize these web services effectively, customer's have to (a) locate each of these services from service directories and retrieve brief service descriptions, (b) analyze service features and evaluate their applicability to the task at hand dynamically, and finally (c) invoke these services in a certain sequence to complete an overall business or personal need. Alternatively, intermediaries execute the aforementioned steps manually and provide a composite service for access from a single service platform. Both these approaches are highly tedious (either for the customer or intermediary) and non-scalable due to the volatility and size of the web. The dynamic nature of the availability and features of web services, real-time requirements on service composition and the large number of alternative combinations of service choices to fulfill a service need makes major demands on the service composition process.This paper presents a novel declarative approach to facilitate dynamic and scalable web service composition called Integrated Service Planning and Execution (ISP&E) based on AI planning techniques. Implementation of an architecture for dynamic web service composition and execution based on a domain-independent AI planning framework called Hierarchical Task Network (HTN) planning is described in this paper. Simulated experiments highlight the effectiveness of our proposed approach which interleaves service composition and execution, to cope with dynamic service capabilities and service volatility.