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

<define name=“cell.content”>

<notAllowed/>

</define>

<start>

<element name="table">
  <oneOrMore>
    <element name="tr">
      <oneOrMore>
        <element name="td">
          <ref name="cell.content"/>
        </element>
      </oneOrMore>
    </element>
  </oneOrMore>
</element>

</start>

</grammar>