On July 2, I posted a query to the list asking for any advice on configuring
to launch external applications for viewing graphic file formats.
After some great advice from Marla Thomas Banks at LC and much
tinkering, I was able to get the pieces working.
Here, then, are my caveats for anyone trying to do the same:

You do need to be aware of the four different pieces that make the launching
possible. They are (with tips noted):

1) NOTATION declaration for the filetype.

        This can either be a part of the DTD - specifically in the eadnotat.ent
        fragment of the EAD.DTD or a part of the declaration subset of
        your specific instance - the section between the  brackets "[ ]" of
        section at the beginning. In either place, you can use the notation
type listed by
        Panorama in its manual for PUBLIC notations -  or use the default
        pattern for SYSTEM notations: <!NOTATION ??? SYSTEM>   (where ??? is the
        abbreviation assigned to your file format - see # 4, below)

2) ENTITY declaration in the SGML document

        This goes in the same place alongside the NOTATION - in the DTD or
        in the declaration subset of the instance. I sensed there might be a
        protocal problem with which went first - the NOTATION or the ENTITY,
        but upon testing this thesis, I found that the order didn't matter.
        A typical ENTITY declaration might look like this:

        <!ENTITY mainlogo SYSTEM "mainlogo.gif" NDATA GIF>

3) ENTITY used in the SGML document

        This can be referenced either as an attribute of an element that
        can be used to call external entities, or, quite simplly, as a direct
        reference in the text, using the format:  &name; (e.g. &mainlogo;)
        they way you would reference an extended character. This method
        allows more flexibility as to where you can put an entity.

4) Panorama setup file entry for your filetype

        This is the step that was the most problematic.
        The setup file gives some examples of entries to launch
        programs, but the suggested text did not work on my system.
        Whereas the entry:

                ENTITY AVI
                  LAUNCH "MPLAYER -play -close \file"

        was suggested, I found I had to declare the complete path,
        along with the file extension (".exe") and that the arguments
        "-play" and "-close" caused the launching procedure to abort.
        So my working entry looked like this:

                ENTITY AVI
                  LAUNCH "c:\sgmlbeta\testing\mplayer.exe \file"

With all of these pieces functioning properly, I have been able to
launch a JPEG viewer, an MPEG viewer, Windows' Mplayer
(for MOV and AVI files), and WRITE - in a multimedia frenzy!

p.s. Be sure to check your spelling and the correlation between the
abbreviations used in all
of the four parts - they can be sneaky and hard to catch.
Timothy Young
Beinecke Rare Book and Manuscript Library
Yale University
New Haven, CT  06520
(203) 432-8131