Information technology tools associated with various educational activities often rely on different models of the needed information, support different cooperative styles, and are based on different media and technologies. The architecture of an open software platform which supports educational activities is presented in this paper. The architecture, which is based on a unifying data model, offers a set of services to control cooperative activities based on either synchronous or asynchronous interaction styles. The software platform built on the proposed architecture can be used for integrating both specialized tools supporting specific educational activities and general purpose tools. The paper introduces the general data model, compares the cost-effective use of communication media with different cooperative styles, and exemplifies the proposed approach with two case studies: an electronic mail-based system for distance tutoring (TEMPO), and a software environment for real-time multimedia conferencing (ImagineDesk). (Contains 23 references.) (AEF)