I have looked at Bernd Krieg-Brükner's proposal for CASL syntax at
http://www.informatik.uni-bremen.de/~agbkb/CoFI/CASL/syntax/syntax.0.2.45.ps
(hereafter referred to as BKB-CASL)
and I am impressed with the work laid down, the thought put into the many
details, and the care which lies behind many of the suggestions.
I have also read (most of) a book on SGML this Easter (Travis, Waldt: The SGML Implementation Guide, Springer 1996). See
http://www.sgmlopen.org/sgml/docs/sgmldesc.htm
for a very brief introduction to SGML, and
http://www.sil.org/sgml/publicSW.html
ftp://ftp.ifi.uio.no/pub/SGML/
for an overview of some free SGML related tools. These include
parsers for SGML, normalisers (tools that will insert standard tokens
where various shorthands have been used), and interfaces to many
common document formatting tools, such as latex.
These readings motivated the following comments.