anchor.diff:      access in the way we usually deal with them."))
   
   (defmethod print-object ((obj parallel-composition) stream)
  -  (format stream "(par~{ ~a~})"
  +  (format stream "(par~{ ~s~})"
             (map-parallel-composition #'identity obj)))
   
   (defun parallel-composition (&rest processes)
  
positive.code: (defmethod print-object ((obj trigger) stream)
    (if (and (slot-boundp obj 'pattern)
             (slot-boundp obj 'process))
      (format stream "(trigger ~a ~a)" (pattern obj) (process obj))
      (call-next-method)))
  
  (defun trigger (pattern process)
  
negative.code:     to be managed."))
  
  (defmethod print-object ((obj restriction) stream)
    (format stream "(new ~s ~s)" (name obj) (process obj)))
  
  (defun restriction (name process)
    (make-instance 'restriction :name name :process process))
  