Although artificial intelligence has been successfully introduced to enhance Education through technologies in the past few years, major challenges still remain. One of them is how to represent the knowledge of intelligent systems. To represent the knowledge of systems to support collaborative learning is particularly challenging because it is based on various learning theories and given the complexity of group learning. The main objective of this work is to introduce an ontological infrastructure on which we can build well-grounded theoretical knowledge based on learning theories and to show how we can use it to develop programs to support intelligent guidance for an effective design of group activities. Keywords. Collaborative learning, ontological engineering, intelligent educational system.