The performance data is used to optimize the models by adjusting element values of {HEAD ~ constituent elements} of {TAIL ~ the models} 
The performance data is used to optimize the models by adjusting element values of { HEAD ~ constituent elements } of { TAIL ~ the models }
OTH OTH 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