A specification of each block in {HEAD ~ a first subset} is obtained from the library and translated into an execution function of {TAIL ~ the software implementation} of the block 
A specification of each block in { HEAD ~ a first subset } is obtained from the library and translated into an execution function of { TAIL ~ the software implementation } of the block
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH