-PreSequence = ps:: Elements
- | (Quoted|Word) ^"::" PreSequence /ws
- > PreSequence ^"/" e /ws
- | PreSequence ^"->" e /ws
+NonTerminal = NonTerminal:: Word ws "=" ws RHS
+ | DropNT:: Word "!" ws "=" ws RHS
+ | Colons:: Word "::" ws "=" ws RHS
+ | Word "*" ws ^"=" ws RHS
+ | Word "*/" Word ws ^"=" ws RHS
+
+RHS:: = ("|":: Sequence +/ (ws "|" ws)) +/ (ws (">" -> ~">") ws)