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: ;
  
  /**** Computation Tree Logic Expressions **************************************/
  bl_ax_operator [Variable current_state]
     returns [Formula result]:
  
     @init
     {
        final Variable next_state;
  
        next_state = VARIABLE_SET.generate_new_state_variable();
     }
  
     (WS)* AX_OPERATOR_KW
        bl_formula[next_state]
     (WS)* R_PAREN
  
     {
        /* TODO */
        $result =
           $bl_formula.forAll
           (
              next_state.in
              (
                 current_state.join
                 (
                    MODEL.get_predicate_as_relation("node_connect")
                 )
              );
           );
     }
  ;
  
  bl_ex_operator [Variable current_state]
     returns [Formula result]:
  
     @init
     {
        final Variable next_state;
  
        next_state = VARIABLE_SET.generate_new_state_variable();
     }
  
     (WS)* EX_OPERATOR_KW
        bl_formula[next_state]
     (WS)* R_PAREN
  
     {
        /* TODO */
        $result =
           $bl_formula.forSome
           (
              next_state.in
              (
                 current_state.join
                 (
                    MODEL.get_predicate_as_relation("node_connect")
                 )
              );
           );
     }
  ;
  
  
  bl_ag_operator [Variable current_state]
     returns [Formula result]:
  
     @init
     {
        final Variable next_state;
  
        next_state = VARIABLE_SET.generate_new_state_variable();
     }
  
     (WS)* AG_OPERATOR_KW
        bl_formula[next_state]
     (WS)* R_PAREN
  
     {
        /* TODO */
        $result =
           Formula.replace /* That does not seem to exist. */
           (
              next_state,
              current_state,
              $bl_formula
           ).and
           (
              $bl_formula.forAll
  