In the parent file, you can separate the chapters into parts to divide them into logical groups. For example, in the parent file, the part tags surround the chapter entities:

<part id="pt-foo">
  <partintro>
  <para>Some text for the part intro</para>
     &CHAPTER; 

     &ANOTHER-CHAPTER;
</part>

If you create a part, include a part introduction describing the contents of the part. For example:

  <part id="pt-setup">
    <title>Getting Setup</title>
    <partintro>
      <para>This section contains information you will need when you first join
	the Docs group. You might need to refer to this part again for
	information such as installing &FC;.</para>
    </partintro>

In the HTML output, a separate HTML page is generated with the part number, title, introduction, and TOC. In the PDF output, the same information about the part is on a separate page.