⊦ (R0 * R1)[rs, cf, af] ↔ (∃ rs0, rs1. rs0 ∪ rs1 = rs ∧ rs0 ∩ rs1 = ∅ ∧ R0[rs0, cf, af] ∧ R1[rs1, cf, af])
[[CONCRETESIMPRULES : ()], [EXTRATERMS : (af, cf, rs, R, o[_∃ xv])]]