A Graph based Tool for Modelling Planning Processes in Building Engineering A. Klinger 1 , M. König 2 and V. Berkhahn 1 1 University of Hannover, Institute of Computer Science in Civil Engineering, Callinstraße 34, 30167 Hannover, Germany; Phone +49 511 7625981, Fax +49 511 7624756, { klinger | berkhahn }@bauinf.uni-hannover.de 2 Bauhaus University Weimar, Professorship “Theoretical Methods for Project Management”, Marienstraße 7, 99423 Weimar, Phone +49 3643 584563, Fax +49 3643 584565, markus.koenig@bauing.uni-weimar.de Abstract The planning process of a building is very complex. Many participants with different technical disciplines are involved and work on certain tasks. To manage the planning process the project leader has to organize participants, tasks and building data. For this purpose modern information and communication technologies can be used very effi- ciently. But these technologies require a formal description of the planning process. Within the research project “Relation Based Process Modelling of Co-operative Building Planning” we have defined a consistent mathematical process model for planning processes and have developed a prototype implementation of an application for modelling these processes. Our project is embedded in the priority program 1103 “Network-based Co-operative Planning Processes in Structural Engineering” promoted by the German Research Foundation (DFG). In this paper we present the mathematical concept of our relational process model and the tool for building up the model and checking the structural consistency and correctness. Introduction The planning process in building engineering can be described by a process model and a product model. The process model describes the planning participants and activities which are related to tasks for building components. The product model covers all data 1