Perception in Multimodal Dialogue Systems : 4th IEEE Tutorial and Research Workshop on Perception and Interactive Technologies for Speech-Based Systems, PIT 2008, Kloster Irsee, Germany, June 16-18, 2008, Proceedings - Elisabeth André, Laila Dybkjær, Wolfgang Minker, Heiko Neumann, Roberto Pieraccini, Michael Weber ((Lecture Notes in Computer Science))