| ⊦ p ∈ links(fid, dnode(md, sdt[str, tree])) ↔ p ∈ links(fid, dnode(md, sdt)) ∨ p ≠ ε ∧ p.head = str ∧ p.tail ∈ links(fid, tree), str ∈ sdt |
p ∈ links(fid, dnode(md, sdt[str, tree])) ⊦ str ∈ sdt, p ∈ links(fid, dnode(md, sdt)), p ≠ ε ∧ p.head = str ∧ p.tail ∈ links(fid, tree)
p ∈ links(fid, dnode(md, sdt)) ∨ p ≠ ε ∧ p.head = str ∧ p.tail ∈ links(fid, tree) ⊦ str ∈ sdt, p ∈ links(fid, dnode(md, sdt[str, tree]))