When a statement is compiled, {HEAD ~ the compiler} generates {TAIL ~ a list} of dependencies, which list is compared with the identification list 
generates
When a statement is compiled , { HEAD ~ the compiler } generates { TAIL ~ a list } of dependencies , which list is compared with the identification list
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH