anchor.diff:  ;; ^ correspondingly, the larch millifoot
   
   
  -(defclass mile (measurement)
  +(defclass us-survey-mile (measurement)
     ()
  +  ;; FIXME: Denote as US Survey Mile [1893] - See previous
     (:metaclass length)
  -  (:print-name . "mile")
  -  (:print-label . "mi")
  +  (:print-name . "mile [1893]")
  +  (:print-label . "mi [1893]")
     (:base-factor . #.(* 5280 1200/3937))
  -  (:symbol . :|mi|)
  +  (:symbol . :|mi_1893|)
  +  (:documentation "US Survey Mile [1893]")
     #+OBJECT-ANNOTATION
     (:annotation
      (:defined_by #i<http://physics.nist.gov/pubs/sp811/>)
      ))
   
  -(register-measurement-class (find-class 'mile))
  +(register-measurement-class (find-class 'us-survey-mile))
   
   
   ;;; %% Angular Measure
  
positive.code: 
  ;; referencing [NIST SP811]
  
  (defclass foot (measurement)
    ;; prototypical, derived measurement unit
    ()
    (:metaclass length)
    (:print-name . "foot")
    (:print-label . "ft")
    (:base-factor . 1200/3937)
    (:symbol . :|ft|)
    #+OBJECT-ANNOTATION
    ;; ^ towards a concept similar to OWL annotation properites
    ;; in an application for annotation of Common Lisp objects,
  
negative.code:    ;; ^ specifically SP811 section B.6 (p. 42)
     ))
  
  (register-measurement-class (find-class 'us-survey-foot))
  
  
  ;; (base-magnitude (make-measurement 1 :|ft|))
  