anchor.diff:  
   fragment
   LIDENTIFIER :;
  +fragment
  +PIDENTIFIER :;
  +fragment
  +AIDENTIFIER :;
   
   UIDENTIFIER 
       :   IdentifierStart IdentifierPart*
  
positive.code: 
  packageName returns [Identifier identifier]
      : LIDENTIFIER
        { $identifier = new Identifier($LIDENTIFIER); }
      ;
  
  typeName returns [Identifier identifier]
  
negative.code:       { $positionalArgument = new PositionalArgument(null);
          Expression e = new Expression(null);
          e.setTerm($stringLiteral.stringLiteral);
          $positionalArgument.setExpression(e); 
          $stringLiteral.stringLiteral.getToken().setType(ASTRING_LITERAL); }
      ;
  
  //special rule for syntactic predicate
  