<triple>
  <boolean>
    <value>prox</value>
    <modifiers>
      <modifier>
        <type>unit</type>
        <comparison>=</comparison>
        <value>element</value>
      </modifier>
      <modifier>
        <type>distance</type>
        <comparison>&gt;</comparison>
        <value>5</value>
      </modifier>
    </modifiers>
  </boolean>
  <leftOperand>
    <searchClause>
      <index>dc.author</index>
      <relation>
        <value>==</value>
      </relation>
      <term>jones</term>
    </searchClause>
  </leftOperand>
  <rightOperand>
    <searchClause>
      <index>title</index>
      <relation>
        <value>&gt;=</value>
      </relation>
      <term>smith</term>
    </searchClause>
  </rightOperand>
</triple>
