Those terrains that grant defensive or offensive bonuses to computer players units should be utilised to the best advantage. In addition computer units should strike where the enemy is weakest and where the most damage can be inflicted at the least loss. Impaling units on heavily fortified positions for nominal gain is best left to real generals in real war and is not a bench mark of intelligent behaviour. To combine everything we need to play a good game in the face of a deceptive and hostile opponent is not a trivial task. Being context free they do not consider interdependencies between their variables.
Intensional systems deal with uncertainty in a context sensitive manner.
They try to model the interdependencies and relevance relationships of the variables in the system. If an extensional system has the rule, if A then B with some certainty factor m. and observes A in its database it will infer something about the state of B regardless of any other knowledge available to it. What we believe about B in this system is dependent on our whole view of the problem and how relevant information interacts. The difference between these two systems boils down to a trade-off between semantic accuracy and computational feasibility. Extensional systems are computationally efficable but semantically clumsy.