PURPOSE: To reduce the rule search of an inferring operation by immediately executing the conclusion of an established rule by using pointer information.

CONSTITUTION: In a forward inference system, the rule having a condition part suited to the content of an object to be inferred is searched by using pointer information A indicating the location of the rule to be retrieved at first. It is preferable that the sequence of the rule is used by the pointer information A. When the rule is selected, the establishment of the rule is verfied, and when the rule is established, the conclusion part is immediately executed, and added to the object to be inferred. Then, the suitability of the condition part of the rule is searched for the new object to be inferred according to pointer information part B, and when the rule is established, the conclusion part is immediately executed. Thus, the comparison of the condition part with the object to be inferred can be reduced by successively selecting the rule, and the useless retrieval can be omitted.