<schema xmlns=“www.ascc.net/xml/schematron” >

<pattern name="Test count">
     <rule context="/*">
          <report test="count(//BBB) = count(//AAA)">O.K.</report>
          <assert test="count(//BBB) &lt;= count(//AAA)">Some AAA are missing</assert>
          <report test="count(//BBB) &lt; count(//AAA)">Some BBB are missing</report>
     </rule>
</pattern>

</schema>