Conditions that test for set membership

You can use conditions to test whether a business term belongs to a set.

The following condition tests whether a customer is in the Silver, Gold, or Platinum category:

if 
	'customer category' is one of {Silver, Gold, Platinum}

The following condition tests whether the rule variable luxury car groups contains the car group that is specified in the current rental agreement. The rule first defines the variable luxury car groups as the set of all car groups with a daily rate higher than a certain value:

definitions
	set 'luxury car groups' to all car groups in 'car groups' 
		where the daily rate of each car group is at least 50;
if
	'luxury car groups' contain the car group of 'current rental agreement'