Here's another link:
http://www.animalhealthchannel.com/newpet/index.shtml
I've had two dogs (currently 3 and a cat) in my home for over 20 years, and one thing I'm fairly certain of is that the above poster is correct. The dogs establish the order (after you) and it may even change throughout their lives.
Good luck to you all and I hope some of this helps!!!