anchor.diff:  ;; -----------------------------------------------------------------------class
   (defclass  x3d-bounded-object ()
     ((bbox-center :initarg :bbox-center
  -                :initform (error ":bbox-center must be specified")
  +                :initform (sf-vec3f 0 0 0)
                   :accessor bbox-center
                   :type sf-vec3f
                   :allocation :instance
                   :documentation "")
      (bbox-size :initarg :bbox-size
  -              :initform (error ":bbox-size must be specified")
  +              :initform (sf-vec3f -1 -1 -1)
                 :accessor bbox-size
                 :type sf-vec3f
                 :allocation :instance
  
positive.code: ;; -----------------------------------------------------------------------class
  (defclass  transform  (x3d-grouping-node)
    ((center :initarg :center
           :initform (error ":center must be specified")
           :accessor center
           :type sf-vec3f
           :allocation :instance
           :documentation "")
     (rotation :initarg :rotation
           :initform (error ":rotation must be specified")
           :accessor rotation
           :type sf-rotation
           :allocation :instance
           :documentation "")
     (scale :initarg :scale
           :initform (error ":scale must be specified")
           :accessor scale
           :type sf-vec3f
           :allocation :instance
           :documentation "")
     (sale-orientation :initarg :sale-orientation
           :initform (error ":sale-orientation must be specified")
           :accessor sale-orientation
           :type sf-rotation
           :allocation :instance
           :documentation "")
     (transation :initarg :transation
           :initform (error ":transation must be specified")
           :accessor transation
           :type sf-vec3f
           :allocation :instance
           :documentation ""))
    (:documentation "
  ISO/IEC 19775-1:2008 (SEE NOTICE.TXT)
  
  
negative.code: ;; -----------------------------------------------------------------------class
  (defclass  x3d-grouping-node (x3d-child-node x3d-bounded-object)
    ((children :initarg :children
               :initform ()
               :accessor children
               :type mf-node
               :allocation :instance
  