to <CODE>MSG_VD_SET_HEAPSPACE_TOKEN</CODE>, 
        the <STRONG>ViewerDialog</STRONG> knows to release this heapspace 
        when it is dismissed.  The upshot of all this: now 
        is a good time to call <CODE>GeodeRequestSpace()</CODE>.</LI>
    <LI>Do some correctness checking on the document.  Check its protocol 
        number.  If your document format has some "magic number" or checksum,
        this would be a good time to check it.</LI>
    <LI>If there's a problem, alert the user and discard 