I’ve been reading "pattern matching in the game of go" by Peter Drake, Jim Levenick, Loring Veenstra and Amanda Venghaus. The paper describes Orego, which uses variable-sized pattern matching with patterns extracted from expert games to play 9x9 games.
The details of the position normalisation are given and very interesting, using a lexical ordering. Unfortunately they seem to be closely tied not just to the board size but to the maximum size of the pattern. It also lacks wildcards and ignores ko.
It would be very interesting to see how much better the system would have worked with thousands (or tens of thousands) of training games rather than 100.
The caption to Figure 3 seems mangled.
"Our interpretation is that patterns extracted from recorded games are useful _assuming a reasonable opponent_. The single pattern players produced such bizarre moves that the games devolved into complicated fights, where patterns are not terribly useful. Rutquist (2000) reported a similar effect in experiments using a genetic algorithm to evolve players capable of defeating the relatively strong GNU Go program."
Peter Drake’s home page: http://www.lclark.edu/~drake/
Orego home page: http://www.lclark.edu/~drake/go/