Option arguments inside a variablelist term

["Dominik G." <jdomg66@gmail.com>]

Hi,

I'm trying to write a manpage for a tool that has a commandline option "-o"
which can take three possible option arguments, namely "html", "xml", or "text".
Expressing this in the synopsis is easy:

<refentry xmlns="http://docbook.org/ns/docbook"; xml:lang="en">
  ...
  <refsynopsisdiv>
    <cmdsynopsis>
      <command>foo</command>
      <arg choice="opt">
        <option>-o</option>
        <group choice="plain">
          <arg choice="plain">html</arg>
          <arg choice="plain">xml</arg>
          <arg choice="plain">text</arg>
        </group>
      </arg>
      ...
    </cmdsynopsis>
  </refsynopsisdiv>

However, I'm using a variablelist in the "Options" section of the manpage for
giving a detailed explanation of each option, here I have a problem, using
<arg> and <group> is not allowed inside <term>, how am I supposed to express
the above?

  <refsect1>
    <title>Options</title>
    <variablelist>
      <varlistentry>
        <term>
          <option>-o</option>
          <!-- what to do here ??? -->
        </term>
      </varlistentry>
      ...
    </variablelist>
  </refsect1>

Working around this like

        <term>
          <option>-o</option>
          <replaceable>output_format</replaceable>
        </term>

seems rather inconsistent and using

        <term>
          <option>-o</option>
          html | xml | text
        </term>

looks also ugly mixing semantics with presentation.
Any ideas, suggestions?