Question

我新的XML专用语言包括元素<figure>，代表插图（图像+标题）。

只要插图引用本地数据库中的某些图像，我只想输入

<figure id="9809" width="full" />

标识图像编号9809及其相关标题。

另一方面，如果图像来自外部，则需要稍微不同的语法：

<figure href="https://some-url-here" width="full">Some ad hoc catpion</figure>

到目前为止，我已经声明了一个结合了两种行为的元素，如下所示：

  <!-- Figures -->
  <xs:simpleType name="FigureWidthEnum">
    <xs:restriction base="xs:token">
      <xs:enumeration value="center" />
      <xs:enumeration value="half" />
      <xs:enumeration value="full" />
    </xs:restriction>
  </xs:simpleType>

  <xs:element name="figure">
    <xs:complexType mixed="true">
      <xs:complexContent>
        <xs:extension base="Inline">
          <xs:attribute name="href" type="URI" />
          <xs:attribute name="id" type="xs:nonNegativeInteger" />
          <xs:attribute name="width" type="FigureWidthEnum" default="full" />
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>

它可以正常工作，但是新鲜的编辑器可以弄乱这3个属性，并键入我不想通过Schema Validator轻松实现的不可能的事情。例如：

<figure id="9809" width="full" href="https://some-unexpected-url">Some unexpected caption that should not be here</figure>

我想为<figure>使用两个完全独立的正弦波，好像我可以用相同的名称声明这两个元素一样：

  <xs:element name="figure">
    <xs:complexType mixed="true">
      <xs:complexContent>
        <xs:extension base="Inline">
          <xs:attribute name="href" type="URI" />
          <xs:attribute name="width" type="FigureWidthEnum" default="full" />
        </xs:extension>
      </xs:complexContent>
    </xs:complexType>
  </xs:element>

  <xs:element name="figure">
    <xs:complexType>
      <xs:attribute name="id" type="xs:nonNegativeInteger" />
      <xs:attribute name="width" type="FigureWidthEnum" default="full" />
    </xs:complexType>
  </xs:element>

实际上是不可能的。

可以通过某种方式完成吗？

Answer 1

是的，使用XSD 1.1可以实现，它提供了专门用于此类要求的<xs:alternative>元素。这是我设计用来完全根据您的需要验证的完整XML模式：

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

  <!-- Figures -->
  <xs:simpleType name="FigureWidthEnum">
  <xs:restriction base="xs:token">
    <xs:enumeration value="center" />
      <xs:enumeration value="half" />
      <xs:enumeration value="full" />
    </xs:restriction>
  </xs:simpleType>

  <!-- stub definition -->
  <xs:complexType name="Inline"/>

  <!-- 'figure' element is declared once, but its type has two alternatives -->
  <xs:element name="figure">

    <!-- The first alternative is selected, when the condition specified
     in 'test' attribute is true. The condition must be a boolean XPath
     expression. The '@id' returns the value of 'id' attribute. However,
     when converted to boolean, it indicates whether 'id' attribute is
     specified at all. The anonymous complexType inside <xs:alternative>
     provides the element type valid for this case.
    -->
    <xs:alternative test="@id">
      <xs:complexType>
        <xs:attribute name="id" type="xs:nonNegativeInteger" />
        <xs:attribute name="width" type="FigureWidthEnum" default="full" />
      </xs:complexType>
    </xs:alternative>

    <!-- The second alternative has no 'test' attribute. That means, it must
     be selected by default, when all other alternatives (with a specified
     test condition) do not pass. Here, the anonymous complexType inside
     <xs:alternative> defines the element type in case of reference:
     when 'href' is present.
    -->
    <xs:alternative>
      <xs:complexType mixed="true">
        <xs:complexContent>
          <xs:extension base="Inline">
            <xs:attribute name="href" type="xs:anyURI" />
            <xs:attribute name="width" type="FigureWidthEnum" default="full" />
          </xs:extension>
        </xs:complexContent>
      </xs:complexType>
    </xs:alternative>
  </xs:element>

  <!-- this element is defined just to test the whole schema in XML below -->
  <xs:element name="figures">
    <xs:complexType>
      <xs:sequence>    
        <xs:element ref="figure" minOccurs="0" maxOccurs="unbounded"/>
      </xs:sequence>    
    </xs:complexType>
  </xs:element>

</xs:schema>

此架构可验证的完整XML文件：

<?xml version="1.0" encoding="UTF-8"?>
<figures>

  <!-- passes validation -->
  <figure id="9809" width="full" />

  <!-- passes validation -->
  <figure width="full" href="https://some-unexpected-url">Some ad hoc caption</figure>

  <!-- does not pass the validation -->
  <figure id="9809" width="full" href="https://some-unexpected-url">
    Some unexpected caption that should not be here
  </figure>

</figures>

验证是使用Apache Xerces 2.11.0（支持XSD 1.1）完成的。

促销附加组件。这些链接对于使用XML模式和WSDL的人可能很有趣：FlexDoc/XML XSDDoc＆WSDLDoc –带有图表的高性能通用XML Schema / WSDL文档生成器

如何声明具有两组不同属性的xs：element？

1 个答案: