<element name="example" xmlns="http://relaxng.org/ns/structure/1.0">

  <zeroOrMore>

    <attribute>

      <anyName>

        <except>

          <name>xml:space</name>

        </except>

      </anyName>

    </attribute>

  </zeroOrMore>

  <optional>

    <attribute name="xml:space">

      <choice>

        <value>default</value>

        <value>preserve</value>

      </choice>

    </attribute>

  </optional>

</element>