Cognos TM1 Rules is nothing more than calculation statements. These calculation statements define how to compute values in the cells of the cube to which the rules are assigned.
Usually, every rule you create will require one or more corresponding feeders. Feeder statements, when used correctly, ensure that the correct values are calculated by your Rules and can significantly impact on the performance of your Rules.
If you use feeder statements in a rule (and you should), the rule must also contain a SKIPCHECK declaration and a FEEDERS declaration. The SKIPCHECK declaration must immediately precede any calculation statements in the rule, while the FEEDERS declaration must precede the feeder statements.