With this validator, you can validate against some internal or external schema. And you can validate some internal test cases or an external file.
Open the file menu and choose one of this item:
You can modify the relax ng content in the editor. You can also write your own schema instead of loading one.
If you have choose to use an internal schema from a test suite, choose on of the provided test file in the combo box in the xml content panel.
Otherwise, you can write your own xml file in the editor, or load one from your disk, choosing the "open xml file" item from the file menu.