{HEAD ~ The program} takes as input an initial data set that contains probabilistic information and returns as output {TAIL ~ a sequence} of elementary operations  
returns
{ HEAD ~ The program } takes as input an initial data set that contains probabilistic information and returns as output { TAIL ~ a sequence } of elementary operations
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH