Terry Winograd is the author of the ShrdluProgram, a classic ArtificialIntelligence program which is sometimes known as "Blocks World". The focus of this program was to be able to understand natural language in the context of a world of blocks.
Terry later refuted the idea that the hard AI problem could be solve by the application of rules to a formal representation. The resulting book UnderstandingComputersAndCognition explains his concerns.
His focus today is on HumanComputerInteraction design, with a focus on the theoretical background and conceptual models.
Terry's homepage is: http://hci.stanford.edu/~winograd/