chapter are two join views that do some
    calculations and some more views using them in turn.  One of the
    two first views is customized later by adding rules for
    <TT
CLASS="COMMAND"
>INSERT</TT
>, <TT
CLASS="COMMAND"
>UPDATE</TT
>, and
    <TT
CLASS="COMMAND"
>DELETE</TT
> operations so that the final result will
    be a view that behaves like a real table with some magic
    functionality.  This is not such a simple example to start from and
    this makes things harder to get into. But it's be