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\title{The Anchor Command \texttt{anch}}
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\begin{document}
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{\LARGE\bfseries{}The Anchor Command \texttt{anch}}
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\par{The didactic \textsc{GELLMU} production system provides a command \texttt{"}\verb+\+\texttt{anch"} for anchors that is parallel to the \textsc{HTML} anchor tag \texttt{"\string<a\string>"}. \ 
}
\par{An example of basic usage is given by the following markup for an anchor to the World Wide Web Consortium (W3C): \begin{menulist}
\item\texttt{}\verb+\+\texttt{anch[href=\texttt{"}http://www.w3.org/\texttt{"}]}\verb+{+\texttt{this\ anchor}\verb+}+\texttt{}
\end{menulist} The markup is used here for this anchor\footnote{URI: http://www.w3.org/}. \ 
}
\par{The \emph{urlanch} command provides a succinct way to insert an anchor whose visible content is the referenced \textsc{URI}.\footnote{The name \emph{urianch} would be more ``correct'' since its content is a \textsc{URI}.} Either of these commands may be used in a display, as here: \begin{center}
\url{http://www.w3.org/}\,.
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}
\par{One may ask whether there is a difference between the use of a macro \emph{Urlanch} defined by  \begin{center}
\texttt{}\verb+\+\texttt{newcommand}\verb+{+\texttt{}\verb+\+\texttt{Urlanch}\verb+}+\texttt{[1]}\verb+{+\texttt{}\verb+\+\texttt{anch[href=\texttt{"}\#1\texttt{"}]}\verb+{+\texttt{}\verb+\+\texttt{path}\verb+{+\texttt{\#1}\verb+}+\texttt{}\verb+}+\texttt{}\verb+}+\texttt{}
\end{center} and \emph{urlanch}. \   The latter is used here: \begin{center}
\url{http://www.w3.org/}\footnote{URI: http://www.w3.org/}\,.
\end{center}
}
\par{There \emph{is} a difference. \   The command \emph{urlanch} corresponds to an \textsc{SGML} element, while anything defined with \emph{newcommand} is fully expanded by the \textsc{GELLMU} syntactic translator before \textsc{SGML} generation. \   This means that the treatment of \emph{urlanch} by a formatter is completely independent of the treatment of \emph{anch} and \emph{path} by a formatter, while the treatment of \emph{Urlanch}, if so defined, is entirely dependent on the formatter's treatment of the other two names. \ 
}
\par{Whether it is sensible to undertake the effort of coding formatters to handle the \textsc{SGML} element \emph{urlanch} in addition to the \textsc{SGML} elements \emph{anch} and \emph{path} depends upon whether or not one imagines that there is at least one hypothetical output format for one's document type that might benefit from independent treatment.\footnote{With the default \textsc{GELLMU} formatter for \LaTeX{}, for example, a footnote is created with \emph{Urlanch} but not with \emph{urlanch}. \  (A footnote might also be avoided by using a different attribute name \emph{Href} instead of \emph{href}, but that still does not make the issue vanish.)}
}
\par{If one thinks about these issues solely in terms of formatting from \textsc{GELLMU} markup to \LaTeX{}, one will come to realize that there are several approaches to the needs traditionally met in the \LaTeX{} world with packages:    \begin{menulist}

\item [{\label{macros}(a)}]
 Using macros such as \emph{newcommand} for \textsc{SGML} generation. \ 

\item [{\label{formatters}(b)}]
 Carefully crafting formatters from one's document                   type to \LaTeX{}. \ 

\item [{\label{packages}(c)}]
 Writing \LaTeX{} packages to ``receive'' various                \textsc{SGML} (or \textsc{XML}, of course) document types.\footnote{In fact, it is generally easier to write formatters for document types that are formally \textsc{XML}. \   On the other hand, writing \textsc{SGML} is easier for authors. \   Since an \textsc{SGML} parser can, for most document types, convert \textsc{SGML} to \textsc{XML}, it is sensible for document types used with \textsc{GELLMU} to have both \textsc{SGML} and \textsc{XML} definitions.}
\end{menulist} 
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