The Language — Rules

Example 3. The root mode

Only XHTML is allowed in the root context. In case there is head or some block or inline element we transit to a different mode.

...
<mode name="root">
  <namespace ns="http://www.w3.org/1999/xhtml">
    <validate schema="http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
      <context path="head" useMode="head"/>
      <context path="div|li|p...all block level elements" useMode="block_inline"/>
      <context path="a|em|span|...all inline elements" useMode="block_inline"/>
    </validate>
  </namespace>
</mode>
...