The difference between rc_need, rc_use, rc_before and rc_after in gentoo

While trying to figure out why libvirtd starts before drbd (which is not good for me, because i have virtual machines on drbd, and autostarting virtual machines does not work this way) i wanted to know what is the difference between gentoo init script dependency keywords "need" "use" "before" and "after". Unfortunately i found no documentation about it anywhere, so i had to find it out myself:

• rc_need: A service which uses another service will only run if the another service is running. For example nfs needs portmap, so if you start nfs, then portmap will start automatically before it. If you stop portmap, nfs will be stopped before it. If you restart portmap, nfs will be stopped before, and started after portmap.
• rc_use: A service which uses another service will be started after the another service during bootup, and stopped before the another service during shutdown. Example: sshd uses logger and net, so sshd will be started before logger starts, and stopped before logger stops. But if you restart the logger it will not restart the ssh daemon.
• rc_after: The service will be started after another service during bootup, but during shutdown it does not need to be stopped before the other service stops. Example: nfs will start after quota.
• rc_before: The service will be started before another service during bootup. Example: iptables will start before network comes up.

I do not know what is the effect of rc_after and rc_before during shutdown.

Update: I found the documentation for baselayout-2: man 8 runscript