The rule engine of Combinum CPQ is non-sequential. This means users are not required to set the parameters of a configuration model in any specific order. The rule engine works independently of the selection sequence, automatically preventing or resolving rule conflicts.

Even though the rule engine is non-sequential, it can sometimes be beneficial to guide inexperienced users by not displaying all options at once. This can be achieved, for example, by utilizing the inclusion expressions for tabs to reveal the next tab only when the user has completed the previous one. You can then use the IsSet() expression function to verify which parameters the user has filled in.

Unidirectional and bidirectional rules

Most rule types consist of a triggering side and an action side, and can therefore be considered unidirectional; once the triggering condition is fulfilled, the action takes place.

However, in the case of assignment rules, which consist of a trigger and actions, the rule engine evaluates which parameters will be set to which values if the rule is triggered. If an assignment would cause a conflict, the rule engine prevents the triggering condition by disallowing the conflicting values when needed. This makes the assignment rule bidirectional.

Another bidirectional rule type is the disallowed combination rule. This rule is activated when it is exactly one step away from being fulfilled, regardless of the order in which the parameters were set. For example, if a disallowed combination rule involves three parameters, the rule activates as soon as two of these parameters are given values that are disallowed to combine. The rule engine then steps in and prevents the remaining parameter from receiving its disallowed value.