Users are given {HEAD ~ specific subsets} of the database information to view at a given time, such as column definitions or {TAIL ~ the primary key definition} 
such as
Users are given { HEAD ~ specific subsets } of the database information to view at a given time , such as column definitions or { TAIL ~ the primary key definition }
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL