doc.layout — Specifies the overall document layout.
      <xsl:param name="doc.layout">coverpage toc frontmatter mainmatter index </xsl:param>
The parameter configures the overall document layout, i.e. it specifies if the document must contain a coverpage, some TOC/LOTs, a frontmatter layout (for metadata/preface/dedication rendering), an index section, etc.
See also the doc.lot.show and
    doc.toc.show parameters to specify the
    content of the TOC/LOTs.