/**
* Creates the left model area.
* @return the component that holds the model tree
*/
private JComponent createModelArea() {
TreeModel treeModel = new UmlModelTreeModel(umlModel);
JTree tree = new JTree(treeModel);
TreeCellRenderer treeCellRenderer = new UmlModelTreeCellRenderer();
tree.setCellRenderer(treeCellRenderer);
JScrollPane spane = new JScrollPane(tree);