anchor.diff:           (
               VARIABLE_SET.get_variable
               (
  -               $var
  +               $var.text
               ).oneOf
               (
                  MODEL.get_type_as_relation($type)
  
positive.code: /******************************************************************************/
  /** Behavioral Level **********************************************************/
  /******************************************************************************/
  /**** First Order Expressions *************************************************/
  bl_and_operator returns [Formula result]:
     (WS)* AND_OPERATOR_KW a=bl_formula b=(bl_formula)+ (WS)* R_PAREN
     {
        /* TODO */
        $result = $a.and($b);
     }
  ;
  
  bl_or_operator returns [Formula result]:
     (WS)* OR_OPERATOR_KW a=bl_formula b=(bl_formula)+ (WS)* R_PAREN
     {
        /* TODO */
        $result = $a.or($b);
     }
  ;
  
  bl_not_operator returns [Formula result]:
     (WS)* NOT_OPERATOR_KW bl_formula (WS)* R_PAREN
     {
        /* TODO */
        $result = $bl_formula.not();
     }
  ;
  
  bl_implies_operator returns [Formula result]:
     (WS)* IMPLIES_OPERATOR_KW a=bl_formula b=bl_formula (WS)* R_PAREN
     {
        /* TODO */
        $result = $a.implies($b);
  
negative.code: ;
  
  /** Special Expressions *******************************************************/
  sl_ctl_verifies_operator
     returns [Formula result]:
  
     @init
     {
        final Variable root_node;
  
        root_node = VARIABLE_SET.generate_new_state_variable();
     }
  
     (WS)* CTL_VERIFIES_OPERATOR_KW
           ps=ID
           f=bl_formula[root_node]
     (WS)* R_PAREN
  
     {
        /* TODO */
  
        $result =
           $f.forSome
           (
              root_node.oneOf
              (
                 MODEL.get_type_as_relation("node").in
                 (
                    VARIABLE_SET.get_variable($ps).join
                    (
                       MODEL.get_predicate_as_relation("start_node")
                    )
                 )
              )
           );
     }
  ;
  
  /**** Formula Definition ******************************************************/
  sl_formula
     returns [Formula result]:
  
     sl_predicate
     {
        $result = $predicate;
     }
  
     | sl_and_operator
     {
        $result = $sl_and_operator;
     }
  
     | sl_or_operator
     {
        $result = $sl_or_operator;
     }
  
     | sl_not_operator
     {
        $result = $sl_not_operator;
     }
  
     | sl_implies_operator
     {
        $result = $sl_implies_operator;
     }
  
     | sl_exists_operator
     {
        $result = $sl_exists_operator;
     }
  
     | sl_forall_operator
     {
        $result = $sl_forall_operator;
     }
  
     | sl_ctl_verifies_operator
     {
        $result = $sl_ctl_verifies_operator;
  