A collaborative system is software which allows several users to work together and carry out collaboration, communication and coordination tasks. To perform these tasks, the users have to be aware of other user’s actions, usually by means of a set of awareness techniques. In previous works, we found by means of empirical studies that the most suitable Requirements Engineering approach to specify the requirements of this kind of systems is the Goal-Oriented one, and more precisely i* approach. In this paper, CSRML (Collaborative Systems Requirements Modelling Language) is presented, an extension of i* to deal with the specification of the requirements of these systems in which the collaboration and the awareness of other users presence / actions are crucial. In order to validate this proposal, a case study has been carried out by modelling a jigsaw activity: a cooperative-learning technique in which students individually do some research in a proposed problem and then they teach each other what they have learned by sharing each individual view of the problem.