module contact_and_attachment
  depends on entity_event_and_action

  sort declarations
    attach :: actions
    detach :: actions
    make_contact :: actions

    collide :: make_contact
      attributes
        intensity : intensity_value 

    property_group :: thing
    property_value :: property_group
    intensity_value :: property_value 

  function declarations
    fluents
      basic
        is_touching : tangible_entity * tangible_entity -> booleans
        is_attached_to : tangible_entity * tangible_entity -> booleans
        abuts : spatial_entity * spatial_entity -> booleans

  object constants
    strong : intensity_value 

  axioms
    is_touching(X, Y) if is_attached_to(X, Y).
    -is_attached_to(X, Y) if -is_touching(X, Y).

    is_touching(X, Y) if is_touching(Y, X).
    -is_touching(X, Y) if -is_touching(Y, X).

    is_attached_to(X, Y) if is_attached_to(Y, X).
    -is_attached_to(X, Y) if -is_attached_to(Y, X).

    abuts(X, Y) if abuts(Y, X).
    -abuts(X, Y) if -abuts(Y, X).
    

    false if instance(X, attach),
             -defined_object(X).

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

    false if instance(X, attach),
             object(X, O1),
             object(X, O2),
             instance(O1, tangible_entity),
             instance(O2, tangible_entity),
             O1 != O2.

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

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

    false if instance(X, attach),
             base(X, B1),
             base(X, B2),
             instance(B1, tangible_entity),
             instance(B2, tangible_entity),
             B1 != B2.

    occurs(X) causes is_attached_to(O, B) if instance(X, attach),
                                             object(X, O),
                                             base(X, B).

    impossible occurs(X) if instance(X, attach),
                            object(X, O),
                            base(X, B),
                            is_attached_to(O, B).


    false if instance(X, detach),
             -defined_object(X).

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

    false if instance(X, detach),
             object(X, O1),
             object(X, O2),
             instance(O1, tangible_entity),
             instance(O2, tangible_entity),
             O1 != O2.

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

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

    false if instance(X, detach),
             base(X, B1),
             base(X, B2),
             instance(B1, tangible_entity),
             instance(B2, tangible_entity),
             B1 != B2.    

    occurs(X) causes -is_attached_to(O, B) if instance(X, attach),
                                             object(X, O),
                                             base(X, B).

    impossible occurs(X) if instance(X, detach),
                            object(X, O),
                            base(X, B),
                            -is_attached_to(O, B).


    false if instance(X, make_contact),
             -defined_object(X).

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

    false if instance(X, make_contact),
             object(X, O1),
             object(X, O2),
             instance(O1, tangible_entity),
             instance(O2, tangible_entity),
             O1 != O2.

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

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

    false if instance(X, make_contact),
             base(X, B1),
             base(X, B2),
             instance(B1, tangible_entity),
             instance(B2, tangible_entity),
             B1 != B2.

    occurs(X) causes is_touching(O, B) if instance(X, make_contact),
                                          object(X, O),
                                          base(X, B).

    occurs(X) causes abuts(O, B) if instance(X, make_contact),
                                    object(X, O),
                                    base(X, B).

    impossible occurs(X) if instance(X, make_contact),
                            object(X, O),
                            base(X, B),
                            is_touching(O, B).

    impossible occurs(X) if instance(X, make_contact),
                            object(X, O),
                            base(X, B),
                            abuts(O, B).


    intensity(X) = strong if instance(X, collide).



    false if instance(X, break_contact),
             -defined_object(X).

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

    false if instance(X, break_contact),
             object(X, O1),
             object(X, O2),
             instance(O1, tangible_entity),
             instance(O2, tangible_entity),
             O1 != O2.

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

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

    false if instance(X, break_contact),
             base(X, B1),
             base(X, B2),
             instance(B1, tangible_entity),
             instance(B2, tangible_entity),
             B1 != B2.

    occurs(X) causes -is_touching(O, B) if instance(X, break_contact),
                                           object(X, O),
                                           base(X, B).

    occurs(X) causes -abuts(O, B) if instance(X, break_contact),
                                     object(X, O),
                                     base(X, B).

    impossible occurs(X) if instance(X, break_contact),
                            object(X, O),
                            base(X, B),
                            -is_touching(O, B).

    impossible occurs(X) if instance(X, break_contact),
                            object(X, O),
                            base(X, B),
                            -abuts(O, B).