msg{-}spec(${\it ds}$;${\it da}$) $\,\equiv$$_{\mbox{\scriptsize def}}$$\;\;$${\it kl}$:Knd$\times$IdLnk fp$\rightarrow$ msg{-}item(${\it ds}$;${\it da}$;1of(${\it kl}$);2of(${\it kl}$)) List