Table 3: A summary of EBNFoperators

X = Y . means "an X is defined to be a Y"

X | Y   means "either an X or a Y"

[ X ]   means 0 or 1 occurrence(s) of an X"

{ X }   means "0 or more occurrences of an X"

also

( )     group sub-expressions

" "     enclose a terminal symbol