module ext_contact_and_attachment
  depends on contact_and_attachment

  function declarations
    fluents
      basic
        is_accessible : entity -> booleans

  axioms
    impossible occurs(X) if instance(X, attach),
                            base(X, B),
                            -is_accessible(B).


    impossible occurs(X) if instance(X, make_contact),
                            object(X, O),
                            base(X, B),
                            location(O, L),
                            -location(B, L).

    impossible occurs(X) if instance(X, make_contact),
                            object(X, O),
                            base(X, B),
                            -location(O, L),
                            location(B, L).