Web Service Composition Based On QoS Awareness

In the current few decades, it is expected that web services will proliferate, many web services will offer the same services, and the clients will demand more value added and informative services rather than those offered by single, isolated web services. As the result, the problem of synthesizing web services of high quality will be raised as a prominent issue.Although these service have the same function, but have different qualities. These web service Typical QoS properties associated with a web service are the execution cost and time, availability, reputation, and so on. Huge number of composition plan will be combined from these services. The clients will face the trouble of choosing or creating composition plans, among numerous possible plans, that satisfy their quality-of-service (QoS) requirements.In engineering perspective, generating the composition plan that fulfills a client's QoS requirement is a time-consuming optimization problem. In this study, we proposed to adopt a variable length chromosome Genetic Algorithm (GA) for handling QoS-aware service composition among multiple paths (multi-path) problem. Our approach uses tree-coding to represent composite services in multiple paths and conducts the gene crossover operation based on service parameters matching. In addition, we build a composition path repository and a set of crossover-point, a formula for selecting the composition path is proposed at the same time. These improved the efficiency and astringency of the algorithm.This study realized the improved genetic algorithm. The superiority of the algorithm is analyzed theoretically and its effectiveness is demonstrated by simulated experimental results.