GOBO::Definable

A role for any kind of entity that can have a definition attached

Typically one would define an GOBO::RelationNode or an GOBO::ClassNode, but not an GOBO::InstanceNode (instances do not have definitions, but they may have descriptions)

There are both textual definitions and logical definitions. A logical definition is an equivalence relationship to an GOBO::ClassExpression. Simple terminology-style ontologies do not have logical definitions.

Is this over-abstraction to use a Role? This could be simply mixed in with Node