public void dispatch(Object sender,String xml){
synchronized (this) {
    history.append(xml);
  }
  dispatchDiagramChangeEvent(sender,xml);
}

public void dispatch ( Object sender , String xml ) { synchronized ( this ) { history . append ( xml ) ; } dispatchDiagramChangeEvent ( sender , xml ) ; }
appends the given string to the history and dispatches the change to all sessions that are listening to this shared diagram .
