spec tcs4 =

data sorts A, B, C < S

ops a: A; b1, b2: B; c: C;

f: A ->? A; g: C->? C

. a = b1 . b2 = c

. forall x: A . not def f(x) . forall x: C . not def g(x);

process f(a) -> SKIP || g(c) -> SKIP