Typically the calculations of eligibility and entitlement stored in the isEligibleTimeline and objectiveTimelines rule attributes may involve complex business calculations, and CER rule classes can be created to structure these calculations in line with business requirements.
Any such rule classes do not need to adhere to any application-supplied interfaces (although the CER "extends" mechanism may be used to create a hierarchy of rule classes to treat rule objects in a polymorphic way if useful).
Some of the calculations will involve accessing stored data, by retrieving rule objects of these types: