Distributed collaborative applications are characterized by supporting groups’ collaborative activities. This kind of applications is branded by physically distributed user groups, who cooperate by interactions and are gathered in work sessions. The effective result of collaboration in a session is the production of simultaneous and concurrent actions. Interactions are fundamental actions of a collaborative session and require being coordinated (synchronized) to avoid inconsistencies. We propose in the present work an event structure based model for coordination in a collaborative session, making possible interactions between participants and applications in a consistent way. The proposed model describes interdependencies, in the form of coordination rules, between different actions of the collaborative session actors.