This book constitutes the refereed proceedings of the 20th International Conference on Advanced Information Systems Engineering, CAiSE 2008, held in Montpellier, France, in June 2008. The 35 revised full papers and 9 revised short papers presented together with 1 keynote lecture were carefully reviewed and selected from 273 submissions. The papers are organized in topical sections on duality and process modelling, interoperability of IS and enterprises, refactoring, information systems in e-government and life-science, knowledge patterns for IS engineering, requirements engineering for IS, conceptual schema modelling, service infrastructure, service evolution, flexible information technologies, metrics and process modelling, information system engineering, and IS development with ubiquitous technologies.