System Name
B2Z list of NLG systems
System Builders Winograd
Development Dates 1972
Languages English
URL (if available)
who's who


The pioneer system capable of answering questions and moving objects within a microworld consisting of variously coloured cubes, blocks, pyramids, and so on. The system answers questions, executes commands, and accepts information in an interactive English dialog. The system contains a parser, a recognition grammar of English, programs for semantic analysis, and a general problem solving system. It can remember and discuss its plans and actions as well as carrying them out. From the generation perspective the interest of the system lies in its dialog capabilities, particularly, for example, the ability to initiate clarification dialogs when references were not clear. Knowledge in the system is represented in the form of procedures, rather than tables of rules or lists of patterns. The system showed natural language, planning and actions working together for the first time in a complete system and would still give some current systems a run for their money!

A 'recreation' of SHRDLU has now been prepared by the Semaphore corporation.


Main reference

Terry Winograd.
Understanding Natural Language.
Academic Press, New York, 1972.

Information last updated: 23.11.2002 (
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