In {TAIL ~ the described embodiment}, {HEAD ~ the ad selection process} is “decoupled” from the ad content delivery process 
In
In { TAIL ~ the described embodiment } , { HEAD ~ the ad selection process } is “ decoupled ” from the ad content delivery process
REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH