The objective of this invention is to provide a system which could make general use of a large set of previously accumulated knowledge data and provide an optimal solution for a problem based on these knowledge data. To achieve the aforesaid objectives, this invention uses state space navigator logic. The fundamental capability of a state space navigator is finding the optimal route in a state space to get from the current state to the target state. A state space is a space whose axes are a number of state variables. The points in this space represent the characteristic states of a system. The actual action from a state space to the next state space is determined according to the knowledge data base which was made based on an actual experience etc.