Chapter 17 HQDM_FRAMEWORK 223 17.7.4 State_of_physical_object A state that is a physical_object or a temporal_part_of a physical_object. EXPRESS specification: *) ENTITY state_of_physical_object SUBTYPE OF(state); SELF\state. temporal_part_of :OPTIONAL SET [1:?] OF physical_ object; SELF\state.member_of :OPTIONAL SET [1:?] OF class_of_ state_of_physical_object; END_ENTITY; (* Attribute definitions: temporal_part_of A temporal_part_of relationship type where a state_of_physical_object may be a