In some complex domains, like the game of Go, evaluating a position is not simple. In other games, like Chess for example, material balance gives good and fast to compute insight on the value of a position. In Go all the stones have the same value, so material balance is not a good heuristic. To evaluate a Go position, a computer needs a lot of knowledge and much more time. Evaluation in computer Go is interesting from an AI point of view, because it shows the power of knowledge in complex and real world domains.