Hi,
I explained main link tables in my blog http://maheshmhetre.blogspot.com/
And to the specific question, to get the model diagram refer the article http://maheshmhetre.blogspot.com/2013/04/windchill-rose-web-publisher.html
This will work for Windchill 9.1 but not sure about the Windchill 10.x. Try and let me know if the model diagram available in 10.x
Regards,
Mahesh