A Framework for Adding Packages to Graph Transformation Approaches Giorgio Busatto 1 , Gregor Engels 2 , Katharina Mehner 2 , and Annika Wagner 2 1 Department of Computer Science, Leiden University P.O. Box 9512, The Netherlands busatto@wi.leidenuniv.nl 2 Department of Computer Science Paderborn University, D-33095, Germany {engels,mehner,awa}@uni-paderborn.de Abstract. Graphs are a commonly used formalism for modeling many different kinds of static and dynamic data. In many applications, data modeling can be improved by using hierarchically structured graphs. But,whiletherealreadyexisthierarchicalgraphdatamodels,nogeneral- purpose hierarchical graph data model exists yet, which unifies common features of these domain-specific models. In this paper, we present graph packages,ageneralformalismfordefininghierarchicalgraphs,supporting the most important features found in known applications. Because of the dynamic nature of graphs, hierarchical graph transfor- mation is also an important issue to be dealt with when using hierar- chical graphs. Motivated by the successful application of graph gram- mars to the specification of graph transformations, we also introduce a framework that allows to specify hierarchical graph transformations by combining existing graph grammar approaches and our graph package concept. These concepts are a step towards the definition of a general- purpose hierarchical graph data model. 1 Introduction Graphs are a very natural and intuitive approach for modeling realistic prob- lems and have been successfully used in different fields of computer science to model, for example, database structures in information systems, data structures in software specification and in programming language semantics, and hypertext structure in hypermedia systems. A graph traditionally consists of a set of nodes and a set of edges, the nodes representing entities of some kind, and the edges representing relations between them. A natural example of graph modeling is the World-Wide Web (WWW), the well-known distributed information system (see [W3]), wherein documents (called pages) contain the actual information, and references between pages (called hyperlinks) represent navigational paths between pages. It is natural to model pages as nodes of a graph, and hyperlinks as edges, thus visualizing the structure of the WWW. H. Ehrig et al. (Eds.): Graph Transformation, LNCS 1764, pp. 352–367, 2000. c  Springer-Verlag Berlin Heidelberg 2000