Data point property
By default, a behavior rule becomes active as soon as the data point assigned to it fulfills a certain condition. So if you want to animate the shape based on a data point property, select Data point property in the Trigger dropdown.
Then define the condition to be applied to the data point with the fields Condition, Function and Value so that the behavior rule takes effect.
Note
Most behavior rules are only evaluated once a data point is placed on them. An exception to this is the action Show object conditionally. This is also evaluated if no data point is placed on it, in which case it is always false. This means that the target object is always hidden if no data point is placed on the corresponding behavior rule.