$\forall$${\it es}$:ES, ${\it Cmd}$:Type, ${\it isupdate}$:(${\it Cmd}$$\rightarrow\mathbb{B}$), ${\it In}$:AbsInterface(${\it Cmd}$), $L$, ${\it L'}$:(E(${\it In}$) List).
\\[0ex]updates($L$ @ ${\it L'}$) $\sim$ (updates($L$) @ updates(${\it L'}$))