This paper presents an analysis of collaborative design activity, explaining how design participants collaborate to achieve integrated design on the basis of sharing and substantiating common generic structures with domain design developments. Referring to a previous observation of teamwork in architectural modelling, an overview of the structnralist approach to collaborative design is firstly introduced. The structuralist scenario is then classified into the aspects of model construction, model-constructing constraints, and modelling acts. By examining the properties of different types of design representations and the systematic relations among them, the constraints on collaboration are identified; a logic of collaborative design is found in the necessity of maintaining a dual correspondence between the evolution of common generic structures and the development of domain design solutions distributed over several sites. Following the constraints derived, a discussion of the basic requirements for computer-based tools to support collaborative design is given. The paper concludes with how the current work can be related to the research carried out in other areas.