Because this model is the ultimate abstraction, Thing Type and Thing do not have any inherent attributes beyond the identifiers, names, and descriptions portrayed earlier. Their more concrete embodiments, Party Type and Party, Geographic Location Type and Geographic Location, et cetera, also only have a few. At either level of abstraction, the most flexible approach to attributes is not to include them in the entity classes directly.
Figure 9-6 shows the template for Thing Characteristic—defined here as a variable, attribute, or parameter whose values would describe instances of Thing Type (including Thing Specification) or Thing. Each Thing Characteristic Value, then, is the fact that a particular Thing Type or Thing