This is a WWW version of a document. You may copy it. How to refer to it. The different ways put different requirements on the software, and also suggest ways it could be used in delivering a course.
Learners can learn just from overhearing other learners in dialogue with teachers.
One calculation people do all the time is to hear another person's question and judge whether they are ahead or behind relative to the state of understanding implied by the question, and by the teacher's response to it. Certainly scientific papers contain very little of it explicitly, while scientists constantly give off such value judgements. The benefit would be to allow the tutor to dispatch more good answers per minute. Only occasionally are human tutors required for truly intelligent feedback. PDG told me how useful it is to have an index into a video.