With the prevalence of Internet, the rapid development of component, middleware and Web services, and the wide application of the Web, the reliability and quality assurance of Web applications have become a very critical problem and a hot research topic. 随着Internet的普及以及组件、中间件和WebServices等技术的迅速发展以及Web的广泛应用,Web应用的可靠性和质量保证成为一个非常关键的问题和研究热点。