anchor.diff:           (or (typep data 'local-time:timestamp)
                (and (stringp data)
                     (chronicity:parse data))))
  -    (validation-error "~A: ~A is not a date"
  +    (validation-error "~A: ~A is not a valid date"
                         (attribute-name attribute)
                         data)))
   
  
positive.code:          (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"))))
       :documentation ,(access:access (cdr prop) "description")))
  
  (defun parse-json-schema-boolean (json-schema)
  
negative.code:      (cond
         ((and (not data-attribute)
               (not (attribute-optional-p schema-attribute)))
          (let ((error-msg (or (attribute-option :attribute-required-message schema-attribute)
                               (format nil "Attribute required: ~a"
                                       (attribute-name schema-attribute)))))
            (validation-error error-msg)))
         ((not data-attribute)
  