Definition: '(' 'def' name = ID ')'; Command: '(' 'command' name = ID type = [Definition | ID] ')';
Command: '(' 'command' name = ID ( (type = [Definition | ID]) | (id = ID) ) ')';
Constant: name = ID; ConstantRef: ref = [Constant|ID]; Term: =>Constant | ConstantRef; Command: '(' 'command' name = ID ( term = Term ) ')';