This paper describes an approach of how to support collaborative modelling tasks. The presented system, Cool Modes, implements the approach using “plug-in” reference frames encapsulating the semantics of the used models. Details on the extensibility of the system and the definition and interpretation of these reference frames and models in the framework are shown and the co-operation support using the underlying MatchMaker communication server is explained. Furthermore, two examples from the domains “System Dynamics modelling” and “Jewish Ceremonies” are given.