Graph Transformation as a Conceptual and Formal Framework 149

Abstract. Distributed software systems are typically built according to a three layer conceptual structure: Objects on the lowest layer are clustered by components on the second layer, which themselves are lo-cated at nodes of a computer network on the third layer. Orthogonal to these three layers, an instance level and a type or schema level are distinguished when modeling these systems. Accordingly, the changes a system experiences during its lifetime can be classied as the system’s dynamic behavior on the instance level and as the evolution of the sys-tem on the schema level. This paper shows how concepts from the area of graph transformation can be applied to provide a conceptual and formal framework for describing the structural and behavioral aspects of such systems