<element name=“number” xmlns=“relaxng.org/ns/structure/1.0”>

<attribute name="val">
   <list>
      <oneOrMore>
         <choice>
            <value>1</value>
            <value>2</value>
            <value>3</value>
         </choice>
      </oneOrMore>
   </list>
</attribute>
<text/>

</element>