This book constitutes the thoroughly refereed post-conference proceedings of the Third International Conference on Fundamentals of Software Engineering, FSEN 2009, held in Kish Island, Iran, in April 2009.
The 22 revised full papers and 5 revised short papers presented together with 3 invited lectures were carefully reviewed and selected from 88 submissions. The topics include models of programs and systems, software specification, validation and verification, software architectures and their description languages, object and multi-agent systems, coordination and feature interaction, integration of formal and informal methods, integration of different formal methods, component-based development, service-oriented development, model checking and theorem proving, software and hardware verification and CASE tools and tool integration.