In this paper, we propose a machine-machine collaboration formalism to support groupware tailorability. Our work is based on the 3C functional model by Ellis that decomposes collaboration between users into communication, coordination and cooperation phases. Through our research, we realized that Web services are powerful distributed components offering the desired tools in order to adapt a groupware system to the real needs of users. Therefore, we use this technology to define a collaboration protocol between machines over the network for implementing tailorability in CSCW systems. A groupware architecture is presented based on the proposed formalism. We argue that a protocol between machines over the internet should be defined in order to exchange common services in real time collaboration.