Abstract: A system for performing collaborative tasks which permits collaborators to determine the form of a model of the collaborative work, to modify the model in the course of the collaborative work, and to use the model to access information related to the collaborative work. A graphical user interface permits collaborators to view the model and the information accessible via the model in various ways as well as to modify the model and the information. Collaborators are organized into groups and a collaborator's group membership determines how the collaborator may access and modify the model and the related information. The information related to the collaborative work includes documents, discussions, email, reminders, and alerts. In a disclosed embodiment of the system, the model is made up of model entities which belong to hierarchies. A model entity may be a member of more than one hierarchy and the different hierarchies are used to provide different views of the model.