🚀 go-pugleaf

During the development of the ODA standards, there was some discussion of
"Alternative Content Representations" which would function much as you
propose -- i.e. along with a grpahic, you might send a raster which could
be printed by those terminals that supported fax but not CGM.

Unfortunately, it was not accepted.

ODA does include a simple text string alternate for a content portion, so
you can have a string that says "picture of polar bear goes here".

Marvin Sirbu