anchor.diff:     ;; ^ specifically SP811 section B.6 (p. 42)
      ))
   
  -(register-measurement-class (find-class 'foot))
  +(register-measurement-class (find-class 'us-survey-foot))
   
   
   ;; (base-magnitude (make-measurement 1 :|ft|))
  
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: ;; ^ correspondingly, the larch millifoot
  
  
  (defclass us-survey-mile (measurement)
    ()
    ;; FIXME: Denote as US Survey Mile [1893] - See previous
    (:metaclass length)
    (:print-name . "mile [1893]")
    (:print-label . "mi [1893]")
    (:base-factor . #.(* 5280 1200/3937))
    (: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 'us-survey-mile))
  
  
  ;;; %% Angular Measure
  