A good sense of the state of the art and difficulties in human-robot dialogue can be gained from (Scheutz et al. 2011). Some of the dialogue examples presented there, concerning boxes and blocks, are reminiscent of Winograd's shrdlu, but they also exhibit the challenges involved in real interaction, such as the changing scenery as the robot moves, speech recognition errors, disfluent and complex multi-clause utterances, perspective-dependent utterances ( “Is the red box to the left of the blue box?”), and deixis  (“Go down there”). In addition, all of this must be integrated with physical action planned so as to fulfill the instructions as understood by the robot. While the ability of recent robots to handle these difficulties to some degree is encouraging, many open problems remain, such as the problems of speech recognition in the presence of noise, better, broader linguistic coverage, parsing, and dialogue handling, adaptation to novel problems, mental modeling of the interlocutor and other humans in the environment, and greater general knowledge about the world and the ability to use it for inference and planning (both at the domain level and the dialogue level).