tRelations = new ArrayList<DataFieldType>();
tRelations.add(oldDataFieldType);
cmd = SetCommand.create(diagram.getEditingDomain(), dft,
(EStructuralFeature) dft.eClass().getEStructuralFeature(
"relation"), tRelations);
diagram.getEditingDomain().getCommandStack().execute(cmd);
oldDataFieldType = dft;