in the last line-the where clause, the rule name (GRANDPARENT_RULE) is upper case; but it is lower case when i inserted it into the rulebase. however, when i updated the rulebase using the lower case rule name, i got '0 row inserted' that means nothing updated. and, the following query returned wrong result. however, if i updated the rulebase using the upper case rule name, i got '1 row inserted' and the query result is correct. i thought the upper case and the lower case should made no difference. can anybody tell me why the results are different? thanks in advance.