anchor.diff:      | CEIL OPEN_BRACE expression CLOSE_BRACE -> ^(CEIL expression)
       | FLOOR OPEN_BRACE expression CLOSE_BRACE -> ^(FLOOR expression)
       | ROUND OPEN_BRACE expression CLOSE_BRACE -> ^(ROUND expression)
  -    | CONCAT OPEN_BRACE expressionList CLOSE_BRACE -> ^(CONCAT expressionList)
  +    | CONCAT expressionList -> ^(CONCAT expressionList)
  +    | subStringExpression -> subStringExpression
       | STRLEN OPEN_BRACE expression CLOSE_BRACE -> ^(STRLEN expression)
       | UCASE OPEN_BRACE expression CLOSE_BRACE -> ^(UCASE expression)
       | LCASE OPEN_BRACE expression CLOSE_BRACE -> ^(LCASE expression)
  
positive.code: CONSTRUCTTRIPLES;
  PROPERTYLIST;
  COLLECTION;
  BLANKNODE;
  TRIPLE;
  SUBJECT;
  PREDICATE;
  
negative.code:     ;
  
  expressionList
      : ( nil | OPEN_BRACE expression ( COMMA expression )* CLOSE_BRACE ) -> ^(EXPRESSIONLIST nil* expression*)
      ;	
  
  constructTemplate
  