The Engine also retrieves product period information from the database, including the start date and end date, and creates a ProductPeriod rule object in memory for each published product period in the system. For a new product, there is typically only one period covering the lifetime of the product, but as new legislation is introduced, then it is possible (depending on design approach) for the product to have more than one period. For more information on adding product periods over time, see Incremental Design and Evolution.
These product periods allow the Engine to identify which ones will contribute to a determination on a case - namely the periods that overlap in any way with the case's lifetime. Other product periods outside the case's lifetime (i.e. before the case started or after it ended) do not contribute. The structure and maintenance of the ProductPeriod rule objects is fixed by the Engine and cannot be customized.