anchor.diff:  ;; -----------------------------------------------------------------------class
   (defclass  x3d-grouping-node (x3d-child-node x3d-bounded-object)
     ((children :initarg :children
  -             :initform (error ":children must be specified")
  +             :initform ()
                :accessor children
                :type mf-node
                :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-bounded-object ()
    ((bbox-center :initarg :bbox-center
                  :initform (sf-vec3f 0 0 0)
                  :accessor bbox-center
                  :type sf-vec3f
                  :allocation :instance
                  :documentation "")
     (bbox-size :initarg :bbox-size
                :initform (sf-vec3f -1 -1 -1)
                :accessor bbox-size
                :type sf-vec3f
                :allocation :instance
  