P5: Guidelines for Electronic Text Encoding and Interchange

<rng:element name="timeline">
<rng:ref name="att.global.attributes"/>
<rng:attribute name="origin">
 <rng:ref name="data.pointer"/>
</rng:attribute>
<rng:optional>
 <rng:attribute name="unit">
  <rng:choice>
   <rng:value>d</rng:value>
   <rng:value>h</rng:value>
   <rng:value>min</rng:value>
   <rng:value>s</rng:value>
   <rng:value>ms</rng:value>
   <rng:data type="Name"/>
  </rng:choice>
 </rng:attribute>
</rng:optional>
<rng:optional>
 <rng:attribute name="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:choice>
 </rng:attribute>
</rng:optional>
<rng:oneOrMore>
 <rng:ref name="when"/>
</rng:oneOrMore>
</rng:element>

element timeline
{
   att.global.attributes,
   attribute origin { data.pointer },
   attribute unit { "d" | "h" | "min" | "s" | "ms" | xsd:Name }?,
   attribute interval
   {
      xsd:float { minExclusive = "0" } | "regular" | "irregular"
   }?,
   when+
}