A server receives an interaction history comprising a set of one to {HEAD ~ one interactions} between {TAIL ~ a first user} and other users 
between
A server receives an interaction history comprising a set of one to { HEAD ~ one interactions } between { TAIL ~ a first user } and other users
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH