General Problem Solver
Newell, Shaw and Simon separated the solving method from the particular problem: the program reduces the difference between the current and the goal state.
Why it matters
Means-ends analysis was the first attempt to describe problem solving in general rather than for one domain.
GPS worked on a problem given as states, operators and a table of differences. It solved puzzles and symbolic transformations, but required a person to describe the space in advance. Simon and Newell treated the program both as an engineering tool and as a model of human thinking.