This book constitutes the refereed proceedings of the 9th International Conference on Object-Oriented Information Systems, OOIS 2003, held in Geneva, Switzerland in September 2003. The 29 revised full papers and 11 revised short papers presented together with an invited paper and abstracts of 2 invited talks were carefully reviewed and selected from 80 submissions. The papers are organized in topical sections on evolution of OOIS, OOIS frameworks, patterns and components, object-oriented databases, XML on Web aspects, evolution, object-oriented design and architecture, and modeling of information systems