Service chain discovery and recommendation are significant in services composition. A complex network module based algorithm using services invocable relations is proposed to search useful service chains on the network. Furthermore, a new scheme for discovering composite services processes automatically and recommending service chains by ranking their QoS is provided. Simulations are carried out and the results indicate that some useful service chains in the dataset provided by the WSC2009 can be found by the new algorithm. 1. Introduction Web service was widely applied for its outstanding advantages like self-describing, self-containing, and easy deployment. In order to implement complex business flow, composition of existing web services is a common way to solve the problem [1]. Web services composition includes a serious of services by service relations and generates a behavior chain to meet user requirements, which is called a web service chain [2]. A service chain should not only satisfy the functional requirements of users but also make sure that all of the services in the chain are correct and reliable. Consequently, how to compose web services to discover service chains according to service relations is very crucial. In web service, the compatibility and integral efficiency of composed services should be considered during the composition procedure of web services. Web services are combined according to the attributes and functions of both services provided and the user requirements [3, 4], especially a lot of works have been proposed in this field of quality-driven web services composition [5–7]. Recently, some researchers have proposed a lot of algorithms using graph theory to discover service composition [8], in which the services and the relations among them are treated as nodes and edges, respectively. In this kind of methods, the composition of web services is achieved by looking for feasible path among the nodes. The flaw of these schemes is that the research on graph theory tends to be theatrical research rather than the actual situation. As a matter of fact, the web services are distributed on the web servers on the Internet, and the basic structure and characteristics of it are more like a complex network. Therefore, the basic architecture model of web services is complex network rather than a graph. In this paper, we firstly analyze the scale-free and small-world features of the complex network we created, which illustrates the basic structure is a complex network. The traditional graph theory cannot reflect the actual distributed
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