It was only twenty years ago that interaction with computers was for the most part only possible through symbols that could be understood exclusively by expert users. Today we can hardly imagine that the interface once did not include the graphical apparatus of icons, buttons, pictures, and diagrams that we have become so accustomed to. But when we interact with computers, we also want them to react to our actions as a cooperative partner and to provide adequate feedback in case of communication flaws. In fact, we want them to be endowed with characteristics that closely mimic human conversation. Whereas the visual interactive qualities of interfaces have improved a lot, computers are still unable to generate the basic communication structures in a similarly powerful and cooperative way as we find in human-human communication. Today’s commercially available systems hardly ever answer questions in a proper way, are unable to argue about particular information, and rarely provide relevant or even truthful feedback in case of communication or other errors.