To provide a recognition system which uses a useful lexical tree in an application whose processing capability is limited.

A dynamic programming technique uses a vocabulary tree that is coded in a computer memory as a flat display in which each generation node occupies adjacent memory positions. A traversal algorithm uses an expression of the traversal rule and a prescribed generation node is processed before the parent node of the prescribed generationg is processed. A deepest child generation is processed first and the traversal between each generation node is progressed in a same topology direction.