Definition
SHRDLU is a natural-language program written by Terry Winograd at MIT in 1968-70. It manipulated a simulated table of geometric blocks and conversed in English about what it was doing — accepting instructions like "Put the small red block on the large green one" and answering questions like "What did the red cube support before?" The system integrated planning, parsing, and a small world model tightly within its closed block world.
Why it matters
How it works
SHRDLU's architecture: a parser converted English into structured semantic representations using procedural grammar rules; a planner decomposed goals into subgoals using means-end analysis; a world model tracked block positions, sizes, colors, and relationships. The components were tightly coupled — the parser called the planner, the planner queried the world model, the world model updated as the planner acted. Implemented in LISP and Micro-Planner, the system was a tour de force of late-1960s symbolic AI.