Conceptual modelling of complex information systems requires the use of a formal design approach covering both static and dynamic aspects of the system and the modelled Universe of Discourse. Viewing an information system as a collection of communicating objects is close to the intuitive perception of such systems on a conceptual level. Objects have a local state, show a specific behaviour, communicate with other objects and may be itself composed from smaller objects. This article presents an abstract concept of such dynamic objects and discusses language features of a specification language for describing object systems. The presented language \sc Troll2 supports structuring mechanisms of semantic data models together with process specification constructs to cover object dynamics. Extensions of the presented framework are discussed covering the step from communicating objects to cooperating agents allowing more flexible system structures.