Process 2000 begins with operation 2002, where {HEAD ~ the reader} retrieves at least a TPK and an ES from {TAIL ~ a tag} 
Process 2000 begins with operation 2002 , where { HEAD ~ the reader } retrieves at least a TPK and an ES from { TAIL ~ a tag }
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL