Abstract
Open systems are complex, heterogeneous systems whose complexity is often handled by component-based approaches. While the internal functioning of such components is invisible to the outside, a great emphasis is put on the verification of properties that ensure a safe, predictable, and understandable external behaviour. At the same time, the rules that govern and describe the system behaviour must guarantee maximum flexibility. Developing technologies that can satisfy the requirements of open multi-agent systems poses an important and difficult challenge. Here, declarative approaches have the potential of offering solutions satisfying the needs for both specifying and developing open multi-agent systems and other open systems for diverse applications such as business processes, clinical guidelines and cloud computing