module releasing_and_confining
  depends on unobstructing_and_obstructing

  sort declarations
    release :: unobstruct
    confine :: obstruct

  function declarations
    fluents 
      basic
        is_confined : tangible_entity -> booleans
        confined_to : tangible_entity * tangible_entity -> booleans

        is_inside : spatial_entity * spatial_entity -> booleans

  axioms
    is_confined(X) if confined_to(X, Y).
    -confined_to(X, Y) if -is_confined(X).

    is_obstructed(X) if is_confined(X).
    -is_obstructed(X) if -is_confined(X).

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

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

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

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

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

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


    occurs(X) causes -confined_to(O, B) if instance(X, release),
                                           object(X, O),
                                           base(X, B).

    occurs(X) causes -is_confined(O) if instance(X, release),
                                        object(X, O),
                                        -defined_base(X).

    occurs(X) causes confined_to(O, B) if instance(X, confine),
                                          object(X, O),
                                          base(X, B).

    occurs(X) causes is_confined(O) if instance(X, confine),
                                       object(X, O),
                                       -defined_base(X).
  

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

    impossible occurs(X) if instance(X, release),
                            object(X, O),
                            base(X, B),
                            -confined(O, B).

    impossible occurs(X) if instance(X, release),
                            object(X, O),
                            -defined_base(X),
                            -is_confined(O).

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

    impossible occurs(X) if instance(X, confine),
                            object(X, O),
                            base(X, B),
                            confined_to(O, B).  

    impossible occurs(X) if instance(X, confine),
                            object(X, O),
                            -defined_base(X),
                            is_confined(O).