Sequence of relation hooks?

[Joseph Heck]

Is there a concise description of which hooks get called, and I'm which order, when two units are related to each other with "add-relation"?

The "provides" and "requires" I can make guesses at, but I wasn't sure about the "peer" type of relation. Something as simple as a sequence diagram would be ideal - I'm just getting a little lost of what gets invoked where during the state change process. 

-joe