M. Knoll, M. Helling, A. Wacker, S. Holzapfel, and T. Weis. Proceedings of the 5th International Workshop on Collaborative Peer-to-Peer Systems, COPS09, organized at the 18th IEEE International Workshops on Enabling Technologies: Infrastructures for Collaborative Enterprises, WETICE 2009, Groningen, The Netherlands, (June 29th - July 1st June 2009)-July 1 st.