Definitions | , Dec(P), Type, ES, P & Q, P   Q, x(s1,s2), f(a), b, E, P  Q, strong-subtype(A;B), t T, s = t, x:A. B(x), x:A B(x), x:A. B(x), x:A B(x), AbsInterface(A), e  X, X(e), x.A(x), case b of inl(x) => s(x) | inr(y) => t(y), inl x , t.1, inr x , , P Q, left + right, can-apply(f;x), do-apply(f;x), True, A, P  Q, False, Top |