Happy New Year!

How would you implement a mechanism that takes arbitrary XHTML <meta> tags and produces document variables? Consider:

    <meta name="journal" content="Nature" />

After running XML setups, the following would write "Nature":

    \documentvariable{journal}

The tricky part is doing this without pre-defining them. Here's a short, self-contained example to help demonstrate:

\startbuffer[xdoc]
<html>
<head>
  <meta content="Milena Marić Einstein" name="author"/>
  <meta content="Annalen der Physik" name="journal"/>
</head>
<body>
</body>
</html>
\stopbuffer

\startxmlsetups xml:xhtml
  \xmlsetsetup{\xmldocument}{*}{-}
  \xmlsetsetup{\xmldocument}{html|body}{xml:*}
  \xmlsetsetup{\xmldocument}{head}{xml:meta}
\stopxmlsetups

\xmlregistersetup{xml:xhtml}

\startxmlsetups xml:html
  % "author" is a special setup, not generalized
  \xmlfilter{#1}{/head/meta[@name='author']/command(xml:author)}

  % What goes here to make this dynamic?
  %\xmlfilter{#1}{/head/meta[@name='journal']/command(xml:journal)}

  \xmlflush{#1}
\stopxmlsetups

\startxmlsetups xml:author
  \setupdocument[author={\xmlatt{#1}{content}}]
  \setupdocument[metadata:author={\xmlatt{#1}{content}}]
  \setupinteraction[author={\documentvariable{author}}]
\stopxmlsetups

% How can this be generalized?
%\startxmlsetups xml:journal
  %\setupdocument[journal={\xmlatt{#1}{content}}]
%\stopxmlsetups

\startxmlsetups xml:body
  \startdocument
    Author: \documentvariable{author}

    \par

    Journal: \documentvariable{journal}
  \stopdocument
\stopxmlsetups

\xmlprocessbuffer{main}{xdoc}{}

Thank you!