TEMPUS S_JEP 07759-945-Modify Symposium on System Modelling, Fault Diagnosis and Fuzzy Logic and Control, May 6-10, 1997, Miskolc, Hungary QUALITATIVE MODELS OF PHYSICAL SYSTEMS - A SURVEY Tamás Mészáros, Gyula Román Technical University of Budapest Department of Measurement and Instrumentation Engineering Muegyetem rkp. 9 H-1521 Budapest, HUNGARY Tel: (36-1) 463-2057 Fax: (36-1) 463-4112 E-mail: {meszaros,roman}@mit.bme.hu Abstract: In the last decade modelling of complex, dynamic systems received distinguished attention. The problem with modelling complex systems is twofold: the system is either too complex to model analytically, or if it can be, the resources needed are not fully available. To amend this problem Qualitative Modelling methods offer solution. The present paper investigates the differences between the analytical and 'empirical' approaches to qualitative modelling and outlines the basic modelling ontology's, also taking into consideration the various qualitative diagnostic methods. Keywords: Qualitative Simulation, Qualitative modelling, Qualitative Diagnosis