| (o[ls(r, x)] * R)[rs, cf, af] ⊦ af(r) = o, r = null |
⊦ (R0 * R1)[rs, cf, af] ↔ (∃ rs0, rs1. rs0 ∪ rs1 = rs ∧ rs0 ∩ rs1 = ∅ ∧ R0[rs0, cf, af] ∧ R1[rs1, cf, af])
∃ rs0, rs1. rs0 ∪ rs1 = rs ∧ rs0 ∩ rs1 = ∅ ∧ o[ls(r, x)][rs0, cf, af] ∧ R[rs1, cf, af] ⊦ af(r) = o, r = null
Used terms: af, cf, rs, R, o[ls(r, x)]