The Engine stores and maintains RateCell rule objects on CER's database tables for cells from certain rate tables. The data from the rate table cells is propagated to these rule objects when modified and is stored in a valueTimeline rule attribute that stores the value of the rate over time. The list of rate tables that are propagated to rule objects is configurable (see Configuration), but otherwise the processing is supplied by the Engine and cannot be customized.
Typically the eligibility and/or entitlement calculations for a product will involve comparisons with or multiplications by rates (in addition to case-specific data); and rules for calculations will access such rates via RateCell rule objects.