test/relaxng/tutor9_4.rng

<grammar xmlns="http://relaxng.org/ns/structure/1.0">
  <start>
    <element name="data">
      <interleave>
        <text/>
	<ref name="inline.class"/>
      </interleave>
    </element>
  </start>

  <define name="inline.class">
    <choice>
      <element name="bold">
        <ref name="inline"/>
      </element>
      <element name="italic">
        <ref name="inline"/>
      </element>
    </choice>
  </define>

  <define name="inline">
    <zeroOrMore>
      <choice>
        <text/>
        <element name="code">
          <ref name="inline"/>
        </element>
        <element name="em">
          <ref name="inline"/>
        </element>
        <!-- etc -->
      </choice>
    </zeroOrMore>
  </define>
</grammar>