This chapter presents a modeling for the Web-Based Cooperative Information Systems (WBCISs). This modeling considers the WBCISs as support of the unavoidable interactions among multiple existing heterogeneous subsystems of the information system and external information sources that share business objects and processes. The WBCIS is considered as an artifact that firstly and mainly allow information exchange, coordination and cooperation among these sources; and secondly data restructing and processes reuse or reengineering. The main concepts are Knowledge Sources and Interaction Component. A knowledge source represents a subsystem of the information system (Personal IS, Workgroup IS or Enterprise IS); or any external information source. The modeling considers the knowledge source as a UML package that presents an interface definition (business objects schema and processes). An interactions component is a kind of Web-based broker of business objects and processes. It is a support for communication services and user-oriented semantic services of the knowledge sources. It is based on the Web so that it deals with semi-structured data and accesses any knowledge source (willing to interact) having its URL. It uses a metadata that describes the knowledge sources as UML package. The modeling specializes interactions components according to the interaction situations of the knowledge source namely interactions for coordination that deal with the consistency of the shared business objects, interactions for cooperation related to the coupled processes’ activities or interactions for transmission that deal with informal and unstructured information exchanges. A Coordination Component allows knowledge source location, access, integration, global view and restructing of the business objects. A Cooperation Component allows process’ activities invocation, reuse or reengineering activities. This methodologic specialization allows easier implementation and reuse of the interaction components. An interaction component is modeled as a UML package.