<when>

<when> indicates a point in time either relative to other elements in the same timeline tag, or absolutely. 16.5.2 Placing Synchronous Events in Time
組件linking — 16 Linking, Segmentation, and Alignment
屬性att.global (@xml:id, @n, @xml:lang, @rend, @rendition, @xml:base, @xml:space) (att.global.linking (@corresp, @synch, @sameAs, @copyOf, @next, @prev, @exclude, @select)) (att.global.analytic (@ana)) (att.global.facs (@facs)) (att.global.change (@change))
absolutesupplies an absolute value for the time.
狀態 非必備的
資料類型 

<rng:ref name="data.temporal.w3c"/>
data.temporal.w3c
unitspecifies the unit of time in which the interval value is expressed, if this is not inherited from the parent timeline.
狀態 非必備的
資料類型 

<rng:ref name="data.enumerated"/>
data.enumerated
被推薦的值包含:
d
(days)
h
(hours)
min
(minutes)
s
(seconds)
ms
(milliseconds)
intervalspecifies the numeric portion of a time interval
狀態 非必備的
資料類型 

<rng:choice>
 <rng:data type="float">
  <rng:param name="minExclusive">0</rng:param>
 </rng:data>
 <rng:value>unknown</rng:value>
</rng:choice>
xsd:float { minExclusive = "0" } | "unknown"
值 a positive number, or the special value unknown.
sinceidentifies the reference point for determining the time of the current when element, which is obtained by adding the interval to the time of the reference point.
狀態 非必備的
資料類型 

<rng:ref name="data.pointer"/>
data.pointer
值 Should point to another when element in the same timeline.
屬於
可包含在於
linking: timeline
可包含空白元素
宣告

<rng:element name="when">
 <rng:ref name="att.global.attributes"/>
 <rng:ref name="att.global.linking.attributes"/>
 <rng:ref name="att.global.analytic.attributes"/>
 <rng:ref name="att.global.facs.attributes"/>
 <rng:ref name="att.global.change.attributes"/>
 <rng:optional>
  <rng:attribute name="absolute">
   <rng:ref name="data.temporal.w3c"/>
  </rng:attribute>
 </rng:optional>
 <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>unknown</rng:value>
   </rng:choice>
  </rng:attribute>
 </rng:optional>
 <rng:optional>
  <rng:attribute name="since">
   <rng:ref name="data.pointer"/>
  </rng:attribute>
 </rng:optional>
 <rng:empty/>
</rng:element>
element when
{
   att.global.attributes,
   att.global.linking.attributes,
   att.global.analytic.attributes,
   att.global.facs.attributes,
   att.global.change.attributes,
   attribute absolute { data.temporal.w3c }?,
   attribute unit { "d" | "h" | "min" | "s" | "ms" | xsd:Name }?,
   attribute interval { xsd:float { minExclusive = "0" } | "unknown" }?,
   attribute since { data.pointer }?,
   empty
}
例子
<when xml:id="TW3" interval="20" since="#w2"/>