How do I create a virtual cube in the mondrian cube framework?

I have two tables through which I need to generate a cube report, I need to display measures from the columns of both tables. I went through the docs on the website and found out that VirtualCube is the way to go if I have to accomplish this feat. However, the document is not very clear and does not have a working example. Can anyone suggest or link to a working example (mondrian.xml file) that might give me some clarity.

Thanks in advance.