anchor.diff:  (defmethod remove-value ((place slot-definition-place))
     (error "not implemented"))
   
  -;;; `class-precedence-list-place'
  -
  -(defclass class-precedence-list-place (read-only-place)
  +;;; `class-list-place'
  +;;;
  +;;; Places of this kind contain a list of classes among which a
  +;;; certain relation such as "subclass" or "superclass" is of
  +;;; interest. As a result, such lists can be shown as a list or as the
  +;;; graph induced by the relation.
  +
  +(defclass class-list-place (read-only-place)
     ())
   
  -(defmethod value ((place class-precedence-list-place))
  -  (c2mop:class-precedence-list (container place)))
  -
  -;;; Object states
  +(macrolet
  +    ((def (name reader
  +           &key (relation reader)
  +                (default-class-list-style :graph))
  +       `(progn
  +          (defclass ,name (class-list-place)
  +            ((%relation                 :allocation :class
  +                                        :reader     relation
  +                                        :initform   #',relation)
  +             (%default-class-list-style :allocation :class
  +                                        :reader     default-class-list-style
  +                                        :initform   ',default-class-list-style)))
  +
  +          (defmethod value ((place ,name))
  +            (,reader (container place))))))
  +  (def subclass-list-place         c2mop:class-direct-subclasses)
  +  (def superclass-list-place       c2mop:class-direct-superclasses)
  +  (def class-precedence-list-place c2mop:class-precedence-list
  +    :relation                 c2mop:class-direct-superclasses
  +    :default-class-list-style list))
  +
  ++
  +;;;; Object states
  +
  +;;; `inspected-slot-definition'
   
   (defclass inspected-slot-definition (inspected-instance)
     ()
  
positive.code: ;;; direct methods
  ;;; add/remove slots
  
  ;;; Place classes
  
  ;;; `slot-definition-place'
  
  
negative.code:           (format-place-cells stream object 'reader-place 'class-name :label "Name")
            (format-place-cells stream object 'reader-place 'class-of :label "Metaclass"))
          (formatting-row (stream)
            (format-place-cells stream object 'superclass-list-place nil
                                :label "Superclasses")
            (format-place-cells stream object 'subclass-list-place nil
                                :label "Subclasses"))
          (when finalizedp ; TODO else display placeholders
            (formatting-row (stream)
  