anchor.diff:           (list :reader (read-from-string (access:access (cdr prop) "x-reader"))))
        ,@(when (access:access (cdr prop) "x-writer")
            (list :writer (read-from-string (access:access (cdr prop) "x-writer"))))
  +     ,@(when (access:access (cdr prop) "x-validator")
  +         (list :validator (read-from-string (access:access (cdr prop) "x-validator"))))
  +     ,@(when (access:access (cdr prop) "x-add-validator")
  +         (list :add-validator (read-from-string (access:access (cdr prop) "x-add-validator"))))
  +     
        :documentation ,(access:access (cdr prop) "description")))
   
   (defun parse-json-schema-boolean (json-schema)
  
positive.code:          (or (typep data 'local-time:timestamp)
               (and (stringp data)
                    (chronicity:parse data))))
      (validation-error "~A: ~A is not a timestamp"
                        (attribute-name attribute)
                        data)))
  
  
negative.code:          (or (typep data 'local-time:timestamp)
               (and (stringp data)
                    (chronicity:parse data))))
      (validation-error "~A: ~A is not a valid timestamp"
                        (attribute-name attribute)
                        data)))
  
  