In this paper, we propose a software architecture based on Web services and Software agents for groupware tailorability. Through our literature study, we realize that the property of tailorability has a significant impact on designing collaborative applications. Although online applications in the recent years have been growing exponentially, online collaborative work between users is often supported by software applications that provide static basic functionalities, mostly centered on communication tools (text, audio and video). Hence, adding more sophisticated tools for enriching the collaborative experience, as for example, an integrated environment for task coordination and production, requires manually coding them into the application, which requires a significant effort in order to adapt the system to the real needs of users. In a collaborative context, the application designers are not able to predict all users' needs at design time. To remedy this problem, we propose a tailorable groupware architecture that enables the dynamic integration/composition of services into the collaborative application, gaining both in time and performance. Our work is based on the 3C functional model by Ellis that decomposes collaboration between users into communication, coordination and cooperation spaces. Through our research, we realized that Web services are powerful distributed components offering the desired tools to adapt a groupware to the real needs of users. In this paper, we propose a collaboration protocol based on Web services between machines over the network in order to exchange common services. Based on this protocol, we propose our groupware architecture, U3D, that introduces tailorability in collaboration applications.