With the introduction of large-scale open systems, the need for managing interactions between agents, and in particular for managing the entry of a new agent into an existing system, becomes an increas- ingly more important objective. Without such management, there may be significant implications for the performance of such systems, negating the benefits to be gained from openness. In this paper, we sketch a pro- cess by which open multi-agent systems may be engineered, through the establishment of a system specification to be used by designers of agents that will enter the system, and by the system itself to check that an agent entering a system complies with the system constraints. While not fully detailed, the paper provides an initial model and a clear direction as to how such a system may be constructed, oering a new way of developing open multi-agent systems.