Implicit selection of a precedence rule's trigger dimension value fires the rule. Under some circumstances, implicit selection of the rule's target dimension value also fires it.
Specifically, when a precedence rule's target dimension value is implicit in the navigation state, and when refinements are available underneath that target dimension value, the precedence rule fires and the target dimension is displayed. This occurs even when none of the rule's trigger values have been implicitly or explicitly selected. The MDEX Engine treats any precedence rules targeting the parent dimensions of these dimension values as having fired, even though the rules' trigger values have not been selected.
For this reason, precedence rule target dimensions may appear when no precedence rule trigger has been selected.