module admitting_and_shutting_out
  depends on unobstructing_and_obstructing

  sort declarations
    admit :: unobstruct
    shut_out :: obstruct

  function declarations
    fluents 
      basic
        shut_out_of : tangible_entity * tangible_entity -> booleans

        is_inside : spatial_entity * spatial_entity -> booleans

      defined
        is_shut_out : tangible_entity -> booleans

  axioms
    is_shut_out(X) if shut_out_of(X, Y).

    is_obstructed(X) if is_shut_out(X).
    -is_obstructed(X) if -is_shut_out(X).


    false if instance(X, admit),
             object(X, O),
             -instance(X, tangible_entity).

    false if instance(X, admit),
             -defined_base(X).

    false if instance(X, admit),
             base(X, B),
             -instance(B, tangible_entity).

    false if instance(X, shut_out),
             object(X, O),
             -instance(X, tangible_entity).

    false if instance(X, shut_out),
             -defined_base(X).

    false if instance(X, shut_out),
             base(X, B),
             -instance(B, tangible_entity).


    occurs(X) causes -shut_out_of(O, B) if instance(X, admit),
                                           object(X, O),
                                           base(X, B).

    occurs(X) causes shut_out_of(O, B) if instance(X, shut_out),
                                          object(X, O),
                                          base(X, B).


    impossible occurs(X) if instance(X, admit),
                            object(X, O),
                            base(X, B),
                            -is_inside(O, B).

    impossible occurs(X) if instance(X, admit),
                            object(X, O),
                            base(X, B),
                            -shut_out_of(O, B).
 
    impossible occurs(X) if instance(X, shut_out),
                            object(X, O),
                            base(X, B),
                            -is_inside(O, B).

    impossible occurs(X) if instance(X, shut_out),
                            object(X, O),
                            base(X, B),
                            shut_out_of(O, B).