# Rules and constraints

In Contact Optimization, you define how optimization behaves by defining different combinations of rules and constraints in a Contact Optimization session.

Most of the time, this guide uses rules and constraints interchangeably and generally calls all rules and constraints within Contact Optimization "rules."

From a strict definition standpoint, rules are requirements that have a single solution. Global exclusions using the Interactions Where rule, or a Never A with B rule, are rules. For a particular set of offers for an individual, the combination is either allowed or it is not. The rule is either true or it is not. For example, an A not following B rule states that offer A cannot be given within 30 days of offer B. The customer, Mr. Jones, who is proposed offer A is either:

• Allowed to receive the offer because he has not received offer B within the last 30 days.
• Not allowed to receive the offer because he has received offer B within the last 30 days.

If Mr. Jones has not received either offer A or B in the past, but is proposed offer A and B, he can receive only one of the offers in any 30-day window. Any proposed offer combinations must satisfy this condition.

A constraint typically specifies a minimum or maximum threshold that cannot be exceeded. There are many possible solutions satisfying the constraint where the goal is to pick the solution that maximizes a particular objective function, for example, maximizing the sum of scores. Constraints might limit contacts by:

• The maximum number of calls the sales team can make in a week
• The amount of marketing activity that is based on the budget
• The pieces of collateral available in inventory

You can create rules with a single answer, such as "If customerA receives a Platinum credit card offer, customerA cannot receive a Gold offer within the same month." You can also create rules with many possible answers. These rules might limit contacts by the maximum number of calls the sales team can make, or the amount of activity that is based on the budget, or the pieces of collateral available in inventory. Furthermore, you can define customer preferences such as contact frequency and channel capacity in rules.