HierarchicalViewContentProvider result = new HierarchicalViewContentProvider();
// need to find the topmost element
if(this.getTotalElementCount() == 0) {
result.element = null;
} else {
HistoryDefinitionLocation dl = (HistoryDefinitionLocation) this.getAllElements()[0];
do {
if(dl.getParent() != null) {
dl = (HistoryDefinitionLocation)dl.getParent();
} else {
break;
}
} while(true);
// topmost element