Each subsystem also includes a blocker coupled to {TAIL ~ a DA} and associated with {HEAD ~ a home directory} 
Each subsystem also includes a blocker coupled to { TAIL ~ a DA } and associated with { HEAD ~ a home directory }
OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD