P5: Directrices para la codificación y el intercambio de textos electrónicos

<rng:define name="data.interval">
 <rng:choice>
  <rng:data type="float">
   <rng:param name="minExclusive">0</rng:param>
  </rng:data>
  <rng:value>regular</rng:value>
  <rng:value>irregular</rng:value>
  <rng:value>unknown</rng:value>
 </rng:choice>
</rng:define>

data.interval =
   xsd:float { minExclusive = "0" } | "regular" | "irregular" | "unknown"