Web environment has shifted from a distributed source of information to a distributed source of service. Service-oriented has become mainstream in software development. Under this case, research to new theory and methodology of software should be carried out. As a new paradigm, web components aims at providing support to service-oriented development by enabling automatic discovery, composition, invocation and interoperation of Services. In this paper, we will discuss various aspects of web components and present a concept model of web components. By means of parameterized contracts, we will discuss the introspection of web components in detail and present an approach of tailoring service.