Advances in Artificial Intelligence 4th Helenic Conference on AI, SETN 2006, Heraklion, Crete, Greece, May 18-20, 2006. Proceedings - Antoniou, Grigoris; Potamias, George; Spyropoulos, Costas; Plexousakis, Dimitris (Springer Berlin Heidelberg : Imprint: Springer, 2006)