R. Neßelrath, and J. Alexandersson. Proceedings of the 6th IJCAI Workshop on Knowledge and Reasoning in Practical Dialogue Systems. Twenty-First International Joint Conference On Artificial Intelligence (IJCAI -09), in Conjunction with 6th IJCAI Workshop on Knowledge and Reasoning in Practical Dialogue Systems (KRPD-09), July 12, Pasadena, California, United States, page 46-51. IJCAI 2009, (July 2009)