Hans-Dieter Ehrich Abteilung Datenbanken, Technische Universitat Postfach 3329, D-38023 Braunschweig, Germany Gunter Saake Institut fur Technische Informationssysteme, Otto-von-Guericke-Universitat Universitatsplatz 2, D-39106 Magdeburg Am'ilcar Sernadas and Cristina Sernadas Departamento de Matem'atica, Instituto Superior T'ecnico Av. Rovisco Pais, P-1096 Lisboa Codex, Portugal 1 Introduction A global information infrastructure is rapidly developing. As a consequence, interest is shifting from local systems to global, widely distributed systems. This implies a growing need for advanced modeling and specification techniques for distributed systems, both for designing new systems and for reengineering old ones. We are concerned with information systems, i.e., reactive systems with the capability of storing and retrieving large amounts of data. Distributed reactive systems are more complex and difficult to specify, analyse, implement and reconfigure than other kinds of systems..