ResourceSet resSet = new ResourceSetImpl();          
Resource res = resSet.getResource(URI.createPlatformResourceURI(targetDiagram.getFullPath().toString(), false), true);

// get the current loaded editor
IWorkbenchPage page = PlatformUI.getWorkbench().getActiveWorkbenchWindow().getActivePage();
		
IGraphicalEditPart ep = (IGraphicalEditPart) page.getActiveEditor();

DiagramEditPart diagramEP = ((DiagramEditDomain) ep.getDiagramEditDomain()).getDiagramEditorPart().getDiagramEditPart();
		
Object st = diagramEP.getChildren().get(0);
ShapeNodeEditPart store = (ShapeNodeEditPart) st;

SelectionRequest request = new SelectionRequest();
request.setLocation(store.getLocation());
request.setModifiers(0);
request.setType(RequestConstants.REQ_OPEN);
store.performRequest(request);

	public static void openLayeredDiagram(LayeredResource lRes) {
		IProject project = ResourcesPlugin.getWorkspace().getRoot().getProject("FN");
		// get the target diagram file
		IFile targetDiagram = project.getFile(resourceFolderLayers + lRes.getRelativePath());
		// try loading it up with Eclipse
		ResourceSet resSet = new ResourceSetImpl();          
		Resource res = resSet.getResource(URI.createPlatformResourceURI(targetDiagram.getFullPath().toString(), false), true);
		IEditorInput editorInput = getEditorInput(res);
		IWorkbenchPage page = PlatformUI.getWorkbench()
		  .getActiveWorkbenchWindow().getActivePage();
		try {
			page.openEditor(editorInput, FnDiagramEditor.ID);
		} catch (PartInitException e) {
			FnDiagramEditorPlugin.getInstance().logError(
					"Exception while openning diagram", e); //$NON-NLS-1$
		}
	}
	
	private static IEditorInput getEditorInput(Resource diagramResource) {
		URI uri = diagramResource.getURI();
		String editorName = uri.lastSegment() + '#'
				+ "Mine test segment";
		IEditorInput editorInput = new URIEditorInput(uri, editorName);
		return editorInput;
	}