implementing SQLXML

I took a run at implementing SQLXML in jdbc4. I have a question about
the getSource method.

It appears that the interface Source implements only two methods
which by themselves aren't very helpful.

There are currently 4 concrete classes that implement the Source
interface, but they seem quite different. It would appear that the
driver will have to do

public Source getSource(Class source)

{
    if instanceof DOMSource return new DOMSource
    if instanceof JAXBSource return new JAXBSource

.....

}

Does this make sense ?

Dave