theorem Th27:
  UsedILoc (I ";" J) = (UsedILoc I) \/ (UsedILoc J)
proof
A1: card(stop Directed I) -' 1 = card Directed I by COMPOS_1:71
      .= card I by SCMFSA6A:36;
  dom I = dom Directed I by FUNCT_4:99;
  then
A2: dom Directed I misses dom (Reloc(J, card I)) by COMPOS_1:48;
  thus UsedILoc (I ";" J)
     = UsedILoc(stop Directed I ';' J)
    .= UsedILoc Directed I \/ UsedILoc Reloc(J, card I) by A2,Th21,A1
    .= (UsedILoc I) \/ UsedILoc Reloc(J, card I) by Th26
    .= (UsedILoc I) \/ (UsedILoc J) by Th25;
end;
