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)
(e1 SUB0 e2 ) ←→ Def (e1 SUB e2 ) ∨ (e1 SUBS e2 ) ∨ (e1 SUBR e2 )