anchor.diff:    "Mutex lock for accessing `%DOMAINS%'")
   
   
  -;;; %% Access Functions
  +;;; %%% Access Functions
   
   (defun register-measurement-class (c)
     (declare (type measurement-class c))
  
positive.code:   (measurement-symbol (class-of instance)))
  
  
  ;;; define core measurement domains and base unit classes
  (let ((kwd (find-package '#:keyword))
        (md-c (find-class 'measurement-domain))
        (mc-c (find-class 'measurement-class))
  
negative.code:              (entity-not-found-name c)))))
  
  
  ;;; %% Measurement Class Storage and Access
  
  ;;; %%% Locking (Thread Safety)
  
  (declaim (type (vector measurement-class) %measurement-classes% ))
  
  