Service-oriented architecture (SOA) is emerging as a paradigm for developing distributed application. As the development of hardware and software technology, fast increasing of peers or services has issued critical problems for the popularity of SOA. One is system scalability and robustness, and the other one is service location validation. In this paper, we introduce-SOBEX -a web service search engine which designs a distributed indexing structure SIKA, and proposes proactive web services reuse mechanism by introducing service context model SPOT. SIKA is a community-oriented virtual hierarchical distributed indexing structure based on classic Chord algorithm. Though it groups nodes into interest-based communities, it is completely distributed and without central management. Then it promises system search efficiency together with scalability and robustness. The growing number of web services available with an organization and on the web raises new problem: locating the desired web services. Generally keyword-based search has meet with high recall and low precision. In order to improve search efficiency, SOBEX proposes to qualify services using service usage context model, which tries to reduce the concept understanding gap between human and computer by proactively assigning the services with their own story background. On the other hand, besides traditional keyword-based methods, it introduces context-based queries to improve service reusability.