"EBNF defined in itself" { syntax = [ title ] "{" { production } "}" [ comment ]. production = identifier "=" expression ( "." | ";" ) . expression = term { "|" term } . term = factor { factor } . factor = identifier | literal | "[" expression "]" | "(" expression ")" | "{" expression "}" . identifier = character { character } . title = literal . comment = literal . literal = "'" character { character } "'" | '"' character { character } '"' . } "EBNF is a cool syntax for describing syntaxes."