Attributes & Values
Isa and instance: class inclusion and membership. More generally an attribute A may be a specialization or generalization of another attribute, e.g. height/physical-size.
Inverses, e.g. has-part/part-of.
Semantics of attribute may restrict value, e.g. average must be a number between .000 and 1.000., age of a person < age of each parent.
Values may be given, computed or inherited.