\documenttype{article}[
\entity{lt CDATA "<"}
\entity{gt CDATA ">"}
\entity{obsl STARTTAG "bsl"}
\entity{oamp STARTTAG "amp"}
\entity{oltc STARTTAG "ltc"}
\entity{ogtc STARTTAG "gtc"}
\entity{foo "a &oltc;sample&ogtc; string"}
\entity{fooglm '&obsl;entity{foo "a &oamp;oltc;sample&oamp;ogtc; string"}'}
\entity{foosgml
   '&oltc;!ENTITY foo "a &oamp;oltc;sample&oamp;ogtc; string"&ogtc;'}
]
\surtitle{The GELLMU Archive}
\title{The Use of SGML Entities in GELLMU}
\author{William F. Hammond}
\date{21 July 2000}

\begin{document}

\section{Introduction}

\abbr{GELLMU} now has provision for the incorporation of an
internal declaration subset with either \abbr{SGML} or direct \abbr{XML}
output from the syntactic translator \softw{gellmu.el}.  (The didatic
\emph{article} document type is first written as \abbr{SGML} and then
re-formatted with some normalization, including \quophrase{argument
naming}, as \abbr{XML}.)

SGML entities do not correspond in any obvious way to classical
LaTeX markup.  However, as things unfold, it is expected that
use of SGML entities may accommodate \emph{some} \latex;-like
macro functionality.

As things stand with the didactic document type, all entity expansion
takes place when the SGML created by \softw{gellmu.el} is first
parsed.

With an appropriate \abbr{SGML} document type defintion, one might
provide for an \quophrase{internal} command in the article preamble
that spawns an internal declaration subset in the \abbr{XML} image.
For direct production of \abbr{XML} this is not an issue.

These two ways of handling entities could be used in the same
document.

\section{A Few Simple Examples}

The quoted phrase at the end of this sentence is produced with entity
markup under the name \emph{foo}: \quophrase{&foo}.  The GELLMU source
used for this phrase is \qquostr{\&foo}.

The \abbr{GELLMU} source for the definition of the entity \emph{foo}
is \display{\verb{&fooglm;}\ \eos} Note that \emph{sample} is not
markup.  The expansion of this definition uses another entity
\emph{fooglm}.  The entity \emph{oltc} is defined in the source with
\display{\verb{\bsl;entity\{oltc STARTTAG "ltc"\}}\ \eos}
It invokes at parse-time the starttag for the empty element \emph{ltc}
in the didactic \abbr{GELLMU} document type that gives rise in most
formattings to the character \quochar{\ltc;}.  Note that this layer of
indirection is only required for an \abbr{SGML} (or \abbr{XML}) document
that is going to be subjected to a formatting pipeline that involves
at least one target language under \abbr{SGML} or \abbr{XML} where
an instance of the character \quochar{\ltc;} might not be intended as markup.

The \abbr{GELLMU} source for the definition of \emph{foo} translates
under \softw{gellmu.el} to SGML as \display{\verb{&foosgml}\ \eos} The
display of this translation is marked up with still another entity
\emph{foosgml}.

\end{document}