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