anchor.diff:  
   occi_headers returns [String header]
     :
  +  {$header = "[";}
     (
  -	    category_header {$header = "[{"+$category_header.category + "}]";}
  -
  -	  | link_header {$header = $link_header.link_header;}
  -
  -	  | attribute_header {$header = $attribute_header.attribute_header;}
  -
  -	  | location_header {$header = $location_header.locations_val;}
  +	    category_header {$header += $category_header.category;}
  +
  +	  | link_header {$header += $link_header.link_header;}
  +
  +	  | attribute_header {$header += $attribute_header.attribute_header;}
  +
  +	  | location_header {$header += $location_header.locations_val;}
     )+
  +  {$header += "]";}
     EOF
   ;
   
  
positive.code:   : LINK_HEADER single_val = link_header_val
      {$link_header = "{\"link\":{" + $single_val.link_header_val + "}}";}
  
    | LINK_HEADER link_header_val (COMMA link_header_val)+
      {;}
  ;
  link_header_val returns [String link_header_val]
    : OPEN_PATH link_path_val CLOSE_PATH rel_attr
  
negative.code: */
  category_header returns [String category]
    : CATEGORY_HEADER category_header_val
      {$category = "{\"category\":{" + $category_header_val.category + "}}"; }
  
    | CATEGORY_HEADER multi_cat1 = category_header_val
      {$category = "{\"category\" : [{"+$multi_cat1.category + "}";}
      (
        COMMA multi_cat2 = category_header_val
        {$category += ", {"+$multi_cat2.category + "}";}
      )+
      {$category += "]}";}
  ;
  category_header_val returns [String category]
    : term_attr scheme_attr class_attr (title_attr | rel_attr | location_attr | cat_attributes_attr | action_attr)*
  