reserve x, x1, x2, y, y1, y2, z, z1, z2 for object, X, X1, X2 for set;
reserve E for non empty set;
reserve e for Element of E;
reserve u, u9, u1, u2, v, v1, v2, w, w1, w2 for Element of E^omega;
reserve F, F1, F2 for Subset of E^omega;
reserve i, k, l, n for Nat;
reserve TS for non empty transition-system over F;
reserve s, s9, s1, s2, t, t1, t2 for Element of TS;
reserve S for Subset of TS;

theorem
  not <%>E in rng dom (the Tran of TS) implies (==>.-relation(TS)
  reduces [x, u], [y, u] implies x = y)
proof
  assume
A1: not <%>E in rng dom (the Tran of TS);
  assume ==>.-relation(TS) reduces [x, u], [y, u];
  then len u > len u or x = y by A1,Th77;
  hence thesis;
end;
