通过XSD限制具有属性的元素数量？

There is a fragment of XML

有一段XML片段

<items>
    <itemUID>uid-1</itemUID>
    <itemUID>uid-2</itemUID>
    <itemUID key="true">uid-3</itemUID>
    <itemUID>uid-4</itemUID>
    <itemUID>uid-5</itemUID>
    <itemUID key="true">uid-6</itemUID>
    <itemUID>uid-7</itemUID>
</items>

Rule: Element items can contain from 1 to unbounded elements itemUID, but only 0 or 2 or 3 elements with attribute key.

规则:元素项可以包含1到*元素itemUID,但只包含0或2或3个带属性键的元素。

Can I define this rule with XSD restrictions only?

我是否可以仅使用XSD限制来定义此规则?

1 个解决方案

#1

You cannot express your constraint in XSD 1.0, but in XSD 1.1, you can use xs:assert to limit the itemUID elements with key attributes to 0, 2, 3 elements as follows:

您无法在XSD 1.0中表达约束,但在XSD 1.1中,您可以使用xs:assert将具有键属性的itemUID元素限制为0,2,3个元素,如下所示:

  <xs:assert test="count(itemUID[@key]) = (0, 2, 3)"/>

Here it is in context in a complete XSD:

这是一个完整的XSD的上下文:

XSD 1.1

<?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="items">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="itemUID" minOccurs="1" maxOccurs="unbounded">
           <xs:complexType>
             <xs:simpleContent>
               <xs:extension base="xs:string">
                 <xs:attribute name="key" type="xs:boolean">
                 </xs:attribute>
               </xs:extension>
             </xs:simpleContent>
           </xs:complexType>
        </xs:element>
      </xs:sequence>
      <xs:assert test="count(itemUID[@key]) = (0, 2, 3)"/>
    </xs:complexType>
  </xs:element>
</xs:schema>