anchor.diff:  
   (defmacro deflibrary (name &body options)
     (destructuring-bind (&key author maintainer description
  -			    license cld versions)
  +			    license cld versions tags)
         options
       `(make-instance 'cld-library
   		    :name ',(if (symbolp name)
  
positive.code: 		    :description ,description
  		    :license ,license
  		    :cld ,cld
  		    :versions ,(parse-cld-library-versions versions))))
  
  (defun parse-cld-library-versions (versions)
    `(list
  
negative.code:    (versions :initarg :versions
  	     :initform (error "Provide a library version at least")
  	     :accessor library-versions
  	     :documentation "The library versions")
     (tags :initarg :tags
  	 :initform nil
  	 :accessor library-tags
  	 :documentation "Library tags"))
    (:documentation "A library meta description"))
  
  (defmethod print-object ((library cld-library) stream)
  