Developing High Quality Data Models

17.1. Thing and Abstract Object

Figure 17-1 shows thing and abstract_object . A thing is anything that exists and is the ultimate supertype of all the other entity types in the schema. The immediate subtypes of thing are individual and abstract_object . The “1” on the subtype graph means that these two entity types are mutually exclusive. A spatio_temporal_extent exists in space and time, while an abstract_object exists in neither space nor time. A thing may be a member__of a class . An abstract_object may be either a class or a relationship , but a relationship may not also be a class .

Figure 17-1 HQDM_FRAMEWORK EXPRESS-G diagram ...