====== SUB0: Generalized Subordination ======

**Definition**: The assertion ''(e1 SUB0 e2)'' describes the most general conceptual subordination. It is defined as a union of the relations [[SUB]], [[SUBS]], and [[SUBR]], i.e. the following holds:
      (e1 SUB0 e2 ) ←→ Def (e1 SUB e2 ) ∨ (e1 SUBS e2 ) ∨ (e1 SUBR e2 )