File		= {Production};
Production	= Nonterminal [ String ] "=" Term ";" ;
Term		= Factor / "|" ;		# alternative
Factor		= ExtAtom + ;			# sequence
ExtAtom		= Atom
		| Atom "/" Atom			# repetion through Atom
		| Atom "+";			# at least one repetion
Atom		= Nonterminal
		| String			# terminal string
		| "(" Term ")"
		| "[" Term "]"			# an optional Term
		| "{" Term "}"			# zero or more repetions
		;
String		= "\"" { Character } "\"" ;
Nonterminal	= letter { letter | digit | "_" | "." } ;
Character       = character
                | ["\\"] anycharacter ;