The stylesheets support list numbering using arabic and roman numerals, as well as uppercase and lowercase letters. If all you want is the numbering style to change for nested orderedlist elements, then the stylesheet already handles that. It nests number styles automatically according to the following sequence:

1, 2, 3
  a, b, c
    i, ii, iii
      A, B, C
        I, II, III

If you want to specify a numbering style for a given orderedlist, then add a numeration attribute to the list as in the following example:

<orderedlist numeration="upperalpha">
  <listitem>
  ...

The allowed values for the numeration attribute are as follows:

arabic
loweralpha
lowerroman
upperalpha
upperroman

If you want to change the order in which these styles are used in nested numbered lists, you need to customize the template named next.numeration located in common/common.xsl. That template takes a numeration name as a parameter, and returns the value that should follow at the next level.

The FO stylesheet also supports the inheritnum="inherit" attribute on an orderedlist. When that attribute is added to an orderedlist that is nested inside another orderedlist, then the inner list's numbering will inherit the outer listitem's number as a prefix. The following example shows how the attribute is used:

<orderedlist>
  <listitem><para>First outer item.</para></listitem>
  <listitem><para>Second outer item.</para>
    <orderedlist inheritnum="inherit">
      <listitem><para>First inner item.</para></listitem>
      ...

This will result in the following print output:

1.  First outer item.
2.  Second outer item.
    2.a.  First inner item.
    ...

This inherit feature does not work for HTML output, because there is no way to specify such a numbering style in HTML markup. It can be done with CSS, though.

When using orderedlists, there may be situations where you need to continue the numbering from one list to the next, with material intervening between them. The stylesheets support the use of the continuation="continues" attribute on the orderedlist element. When that attribute is added, that list will not start number 1, but will instead continue from the end of the closest previous orderedlist in the document. The following example shows how to mark up your document:

<orderedlist>
  <listitem><para>First item in first list</para></listitem>
  <listitem><para>Second item in first list</para></listitem>
</orderedlist>
(other content)
<orderedlist continuation="continues">
  <listitem><para>First item in continued list</para></listitem>
  <listitem><para>Second item in continued list</para></listitem>
</orderedlist>

This will result in the following output:

1. First item in first list
2. Second item in first list
(other content)
3. First item in continued list
4. Second item in continued list

The continuation feature does work in HTML output as well.

When using orderedlist, there may be situations where you need to manually set the starting number for a list. You can do that with an override attribute on the first listitem element, as in the following example:

<orderedlist>
  <listitem override="8">
  ...

The stylesheet will number the first list item with 8 and continue from there. This attribute will override a continuation="continues" attribute if there is one on the same list.