用属性值验证元素值

Question

<list count="3">foo bar baz</list>

有没有什么方法可以检查list元素是否包含3个元素，就像在属性count所说的那样？

Answer 1

XSD 1.0 alone cannot enforce this constraint, but XSD 1.1 can via xs:assert :

<?xml version="1.0" encoding="UTF-8"?>
<xs:schema attributeFormDefault="unqualified" 
           elementFormDefault="qualified" 
           xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:vc="http://www.w3.org/2007/XMLSchema-versioning"
           vc:minVersion="1.1">

  <xs:element name="list">
    <xs:complexType>
    <xs:simpleContent>
      <xs:extension base="xs:string">
        <xs:attribute name="count" use="required" type="xs:int"/>        
        <xs:assert test="count(tokenize(., ' ')) = @count"/>
      </xs:extension>
    </xs:simpleContent>
    </xs:complexType>
  </xs:element>
</xs:schema>