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