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