In one embodiment, {HEAD ~ each global interface} includes a request agent , {TAIL ~ a directory agent} and a slave agent  
includes
In one embodiment , { HEAD ~ each global interface } includes a request agent , { TAIL ~ a directory agent } and a slave agent
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH