Present-day computer-based information systems are increasingly required to be open systems. This means that they must cope with open networks, heterogeneous interoperable hardware and software systems, and, above all, evolving and changing requirements. The CHASSIS project aims to develop a software and methodology framework for (i) the security- and reliability-oriented systematic design and construction of heterogeneous information systems from individual existing and newly developed application software components and database systems, and (ii) their secure and reliable interoperation. In CHASSIS, object-orientation is the key technology for the construction of such a system as its uniform interface is realized by an object-oriented data model and the homogenization layer is realized by object-oriented software. CHASSIS includes object models for database and language integration, software to support system integration, specification methods to support the design process and advanced security mechanisms to provide the resulting information system with a high degree of security. CHASSIS is a joint Swiss project between the University of Zürich, the University of Geneva, and the Asea Brown Boveri Research Centre (Baden).