anchor.diff:  
   (defgeneric class-transform-type (class))
   
  -(defclass transform-class (standard-class)
  -  ((transform-type ;; ?
  -    :initarg :transform-type
  -    :type string
  -    :accessor class-transform-type)))
  -
  -(defclass uml-transform-class (transform-class)
  -   ((uml-name :initarg :uml-name :type string) ;; must map to XML local name
  -    (uml-package :initarg :uml-package)
  -    ;; ^ FIXME: define package structure and ensure referencing to
  -    ;; this slot
  -    ))
   
   ;;; * Element transformation proto.
   
  
positive.code:     :initarg :owned-comments
      :type property-table
      :accessor class-direct-owned-comments-table))
    (:metaclass uml-class)
    (:model *uml-stub-metamodel*)
    (:namespace
     ("uml" "http://www.omg.org/spec/UML/20110701" ))
    (:uml-name "UML::Element")
    (:is-abstract . t))
  
  
  (defclass named-element (element)
  
negative.code:     :accessor transformation-model-namespaces
      )
     (ns-registry
      :type namespace-registry
      :accessor tranformation-model-ns-registry)
     ))
  
  (defmethod shared-initialize :after ((instance transformation-model)
  				     slots &rest initargs
  				     &key &allow-other-keys)
    (when (or (not (slot-boundp instance 'ns-registry))
  	    (and (listp slots)
  		 (member 'ns-registry (the list slots) :test #'eq)))
      (cond
        ((slot-boundp instance 'namespaces)
         (let ((namespaces (slot-value instance  'namespaces)))
  	 (when namespaces
  	   (let ((nsreg (make-namespace-registry)))
  	     (dolist (ns namespaces)
  	       (destructuring-bind (prefix . uri) ns
  		 ;; FIXME: integrate further with qname utils, when
  		 ;; adding elements to the transformation model, etc -
  		 ;; avoid duplcation of qname strings, esp.
  		 (ensure-prefix prefix uri nsreg)))
  	     (setf (tranformation-model-ns-registry instance)
  		   nsreg)))))
        (t
         (simple-style-warning
  	"Instance 'namespaces' slot not bound, unable to initialize ~
  ns-registry slot, in ~s"
  	instance)))))
  
  
  (defgeneric add-transformation (transformation model))
  