In addition to the four primary Logic Rules, default truth states can be specified. These defaults guide the customer, but can be overridden during feature and option selection as the customer makes more refined choices. More complex combinations of these rules can be articulated through an advanced expression editor. Numeric Rules Numeric Rules set and maintain the quantitative modeling parameters specified in the Model structure. Numeric Rules can be assigned to features and options that accumulate a value contributing to a total such as weight, or to suppliers or consumers of resources such as card bays and the peripherals that require slots in them.
Totals are either constants or are set as a result of option selections.
A typical example would be total weight. As an option is selected, the property value for the element's weight is added to the total weight in the configuration. Resources are often used to ensure conservation of a quantity through the course of the configuration. For example, computer configurations have a card cage with a limited number of card slots for hardware and peripherals. The card cage is a resource that supplies a distinct number of card slots.