<constraint>

<constraint> (constraint rules) the formal rules of a constraint
組件 tagdocs — 22 Documentation Elements
屬於
constraintSpec
可包含 空白元素
宣告 

<rng:element name="constraint">
 <rng:ref name="att.global.attributes"/>
 <rng:choice>
  <rng:text/>
  <rng:ref name="macro.anyXML"/>
 </rng:choice>
</rng:element>
element constraint { att.global.attributes, ( text | macro.anyXML ) }
例子
<constraintSpec ident="local" scheme="private">
 <constraint>
   (output = (ident(title) ident(author) "You must supply a title or an author"))
 </constraint>
</constraintSpec>