anchor.diff:       (format s "No measurement class registered for name ~S"
                (entity-condition-name c)))))
   
  +(define-condition measurement-class-redefinition (redefinition-condition)
  +  ()
  +  (:report 
  +   (lambda (c s)
  +     ;; FIXME: #I18N
  +     (let* ((p (redefinition-condition-previous-object c))
  +	    (n (redefinition-condition-new-object c))
  +	    (sym (measurement-domain-symbol p)))
  +       (format s "~<Redefining measurement class ~S~> ~<(previous: ~S)~> ~<(new: ~S)~>"
  +               sym n p)))))
   
   (defclass linear-measurement-class (measurement-class)
  +  ;; FIXME: Reconsider necessity of this class' definition
  +  
     ;; This class is defined, here, for purpose of convenience. 
     ;; See also:  
     ;; `GEOMETRIC-MEASUREMENT-CLASS'
  
positive.code: 			:key #'measurement-symbol)))
        (finalize-inheritance %c)
        (cond 
  	(n (unless (eq (aref %measurement-classes% n) %c)
               (simple-style-warning 
                "Redfining measurement class for ~S" s)
               (setf (aref %measurement-classes% n) %c)))
  	(t (vector-push-extend %c %measurement-classes%)))
        (let ((base-ftor (measurement-base-factor %c))
  	    (base-ftor-exp (measurement-base-factor-exponent %c)))
  
negative.code: 
  (defgeneric measurement-base-factor (measurement))
  (defgeneric measurement-base-factor-exponent (measurement))
  ;; ^ FIXME: Clarify applications of those generic functions
  
  ;;; % Measurement Class
  
  