Distance education is practised in all parts of the world to provide study opportunities for those who cannot-or do not want to-take part in classroom teaching. This does not mean that there is universal agreement about its characteristics. To some, distance education is identical to private study of prescribed texts with or without special study guides, to others, it is a teaching-learning system including specially prepared study materials and regular, mediated contacts between students and tutors, individually or in groups. There are distance-teaching universities that offer their students printed and recorded courses but no mediated communication, although they sometimes provide supplementary face-to-face teaching. This applies, for example, to the Dutch Open Universiteit and the Colombian Unisur. Others like the British Open University, make provision not only for course materials but also for correspondence, telephone and computer communication between students and tutors and others in the distance-teaching school or university, which-following Delling (1987b) and earlier-I call the supporting organization. This use of pre-produced course materials and non-contiguous communication, sometimes supplemented by face-to-face contacts, no doubt represents the praxis of most distance-teaching institutions in the world. In some cases arrangements are also made for peergroup interaction, i.e. for individual students communicating with other students.
Usually students learn entirely individually and at their own pace. They then neither belong to a group or class, nor feel that they do so. A great number of exceptions to this rule occur, however. Universities sometimes teach some groups of students by distance-education methods and other groups face-to-face-