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