Request: Better description of when API hooks are called

The current documentation for hooks doesn't really make clear under what circumstances certain hooks are called. I had some trouble understanding when/if hook_load and hook_validate get called under various circumstances. As it stands, I still can't get hook_validate to be invoked.

The same is true with nodeapi - sometimes certain operations get called, and other times they don't. But the current version of the nodeapi documentation suggests that all of the functions get called in the same order every time. And as with the hook_ problem above, I can't get the "validate" $op to trigger at all.