<grammar xmlns=“relaxng.org/ns/structure/1.0”>

<start>
  <element name="p">
    <ref name="inline"/>
  </element>
</start>

<define name="inline">
  <zeroOrMore>
    <choice>
      <text/>
      <element name="bold">
        <ref name="inline"/>
      </element>
      <element name="italic">
        <ref name="inline"/>
      </element>
      <element name="span">
        <optional>
          <attribute name="style"/>
        </optional>
        <ref name="inline"/>
      </element>
    </choice>
  </zeroOrMore>
</define>

</grammar>