A Universe contextualizes a Unit Type by providing additional restriction characteristics. The class Universe covers both the GSIM 1.2 obects of Universe and Population, conflating them into a single class. A universe may be organized into hierarchical sub-universes. In addition to the standard name, label, and description, the universe may provide a generation code (how the universe is differentiated or split out from another universe), a definition of hierarchical sub-settings for the universe, and an attribute that indicates if the description of the universe is stated in terms of what the universe includes. DDI Lifecycle does not have a Population class as found in GSIM 1.2. It extends the definition of a Universe to include specification of time and geography in contextualizing a Unit Type. In GSIM 1.2 a Universe is a defined class of people, entities, events, or objects with no specification of time and geography, contextualizing a Unit Type. A Population refines a Universe by specifying time and/or geography.