Artificial Intelligence Research Laboratory, Computer Science Department, Iowa State University, Ames, IA 50010, USA. cornelia@cs.iastate.edu|Artificial Intelligence Research Laboratory, Computer Science Department, Iowa State University, Ames, IA 50010, USA. cornelia@cs.iastate.edu|Artificial Intelligence Research Laboratory, Computer Science Department, Iowa State University, Ames, IA 50010, USA. cornelia@cs.iastate.edu|Artificial Intelligence Research Laboratory, Computer Science Department, Iowa State University, Ames, IA 50010, USA. cornelia@cs.iastate.edu