A model for processes of abstraction, based on epistemic actions, has been proposed elsewhere. Here we apply this model to processes in which groups of individual students construct shared knowledge and consolidate it. The data emphasizes the interactive flow of knowledge from one student to the others in the group, until they reach a shared knowledge--a common basis of knowledge which allows them to continue the construction of further knowledge in the same topic together. (Contains 5 figures.) [This research was supported by the Israel Science Foundation.]