5. The knowledge base system according to claim 1 , wherein said operation unit is configured to, when one entity is designated as an operation target, perform the logic operation on an attribute of the designated entity.
8. The knowledge base system according to claim 5 , wherein each attribute is associated with a true-false value indicating whether the attribute is true or false, and said operation unit is further configured to, when one attribute set including one or more attributes is designated, perform a NOT operation of generating a new attribute set with the true-false value being changed, by generating, for each attribute included in the attribute set, an attribute by changing the true-false value to false in a case where the associated true-false value is true and changing the true-false value to true in a case where the associated true-false value is false.