XSD:仅限制一个子元素具有特定值 [英] XSD: Restrict only one child element to have specific value

问题描述

我有一个 XML 读取

I have a XML which reads

<Options>
  <option1>Y</option1>
  <option2>N</option2>
  <option3>N</option3>
</Options>

我想确保只有一个子元素(选项)具有值 Y，这样上面的 XML 是有效的，但下面的无效.

I would like to ensure only one child element (of Options) has value Y so that above XML is valid but not the below one.

<Options>
  <option1>Y</option1>
  <option2>Y</option2>
  <option3>N</option3>
</Options>

我尝试了独特的参照完整性，但没有成功.

I tried unique and referential integrity but couldn't work out.

非常感谢任何帮助/想法.

Any help/idea much appreciated.

推荐答案

您必须在 XSD 1.0 之外强制实施这样的约束，但您可以使用 xs:assert 来强制实施它 <强>XSD 1.1:

You'd have to enforce such a constraint outside of XSD 1.0, but you could use xs:assert to enforce it with 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="Options">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="option1"/>
        <xs:element name="option2"/>
        <xs:element name="option3"/>
      </xs:sequence>
      <xs:assert test="count(* = 'Y') = 1"/>
    </xs:complexType>
  </xs:element>
 </xs:schema>

或者，避免单独命名每个option:

<?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="Options">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="option" maxOccurs="unbounded" />
      </xs:sequence>
      <xs:assert test="count(option = 'Y') = 1"/>
    </xs:complexType>
  </xs:element>
 </xs:schema>

如果需要，当然也可以将选项限制为只有 Y 或 N.

Constraining options to be only Y or N could of course also been done if desired.

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