P5: Linee guida per la codifica e l'interscambio del testo elettronico

<rng:element name="cond">
<rng:ref name="att.global.attributes"/>
<rng:group>
 <rng:choice>
  <rng:ref name="fs"/>
  <rng:ref name="f"/>
 </rng:choice>
 <rng:ref name="then"/>
 <rng:choice>
  <rng:ref name="fs"/>
  <rng:ref name="f"/>
 </rng:choice>
</rng:group>
</rng:element>

element cond { att.global.attributes, ( ( fs | f ), then, ( fs | f ) ) }