<syntax> ::= <rule> | <rule> <syntax> <rule> ::= <opt-whitespace> "<" <rule-name> ">" <opt-whitespace> "::=" <opt-whitespace> <expression> <line-end> <opt-whitespace> ::= " " <opt-whitespace> | "" <expression> ::= <list> | <list> <opt-whitespace> "|" <opt-whitespace> <expression> <line-end> ::= <opt-whitespace> <EOL> | <line-end> <line-end> <list> ::= <term> | <term> <opt-whitespace> <list> <term> ::= <literal> | "<" <rule-name> ">" <literal> ::= '"' <text> '"' | "'" <text> "'"