Automatic Web service composition driven by keyword query

Service-based systems (SBSs) reuse existing loosely coupled Web services to provide value-added composite ones, which brings about much flexibility when the business changes frequently. The advent of automatic Web service composition technology allows system designers to quickly build SBSs without having to manually create process models. Despite the large number of strategies proposed so far, most of them compose Web services through the user-provided initial inputs and expected target outputs, which is not convenient for users to express their functional requirements. To address this issue, we allow users to employ keywords to represent key tasks of the composed Web services. To automatically compose Web services based on the given keywords, we study a new problem of keyword search in the AND/OR graph constructed through semantically matching input-output interfaces of existing related Web services. Due to the complexity of the problem, we propose a heuristic search approach, called UP-DFS. To improve the performance of UP-DFS, we further design two types of pruning strategies. The empirical study shows that our approach can efficiently generate a semantic input-output-based Web service composition that contains all the key tasks in the right order required by users while minimizing the number of services in the composition.