PURPOSE: To shorten time for collating patterns by effectively using the result of pattern collation.

CONSTITUTION: When a rule selecting means 13 selects a rule having high possibility to be started among respective rules stored in a knowledge base 12, a pattern collating means 14 performs pattern collation between the condition part of this selected rule and data. The collated result of this pattern collation is stored in memories 16 and 17. Based on data stored in these memories 16 and 17, a collating condition managing means 15 manages and corrects data to be changed by rule execution among data stored in the memories 16 and 17 after the operation part of the rule is executed, and information showing how much the pattern collation is progressed concerning respective rules is recorded and updated as the collating condition. Then, the cycle of recognition- execution is repeated until no rule in which the condition part of rule and data are matched is in existence.