theorem
  for f being Assign of BASSModel(R,BASSIGN), X being Subset of S holds (
  TransEG(f)).X = SIGMA(f) /\ Pred(X,R)
proof
  let f be Assign of BASSModel(R,BASSIGN);
  let X be Subset of S;
  set g = Tau(X,R,BASSIGN);
  (TransEG(f)).X = SigFaxTau(f,X,R,BASSIGN) by Def70
    .= SIGMA(f) /\ SIGMA(EX(g)) by Th33
    .= SIGMA(f) /\ Pred(SIGMA(g),R) by Th50;
  hence thesis by Th32;
end;
