Session obj_sess;

start(DBData data)
  obj_sess.begin
  db_open_commit_close(data, self.db_finished, obj_sess);

stop()
  obj_sess.end

db_finished(Session cur)
  if(cur != obj_sess)
    return
  emit opened()
  if(cur != obj_sess)
    return
  emit committed()
  if(cur != obj_sess)
    return
  emit closed()