One of the distinguishing features of novel network based learning environments is their capability to support group work and collaboration. TAGS, the Tutor and Groups Support Scheme, is an inter-disciplinary, inter-institutional project, which brings together software systems builders, subject-specialists and educational content developers. Collaborative Learning is central to the pedagogical goals of TAGS, and this has lead to the concept of groups being used as a fundamental organising principle. Groups form the basis of (i) privileges and access control, (ii) information dissemination and event awareness, (iii) teamwork involving shared, multi-user educational resources, (iv) online management of group learning, (v) user-centric portal generation, and (vi) replicated servers. The technical implications of this heavy reliance on the group abstraction are described.