具有相同名称但不同属性值的元素序列的 XML 模式?

注意 正如 Serge 指出的那样，这个答案是不正确的.

NOTE this answer is incorrect, as Serge pointed out.

使用 xerces 进行测试会出现以下错误:type.xsd:3:21: cos-element-consistent: Error for type '#AnonType_productinfo'.具有不同类型的名称为informationset"的多个元素出现在模型组中.cos-element-consistent.

Testing with xerces gives this error: type.xsd:3:21: cos-element-consistent: Error for type '#AnonType_productinfo'. Multiple elements with name 'informationset', with different types, appear in the model group. There's more detail in the spec for cos-element-consistent.

但是有一个解决方案，类似于下面 Marc 的回答，但仍然使用类型.如果它们在由其他类型扩展的超类型的 minOccurs/maxOccurs 列表中，则可以多次出现相同的不同类型.也就是说，就像 java 或 C# 中的多态类列表一样.这克服了上述问题，因为尽管该元素名称可以在 xml 中出现多次，但在 xsd 中只出现一次.

But there's a solution, similar to Marc's answer below, but still using types. It is possible to have multiple occurrences of the same with different types, if they are in a minOccurs/maxOccurs list of a supertype, which is extended by the other types. That is, just like a list of polymorphic classes in java or C#. This overcomes the problem above because although that element name can appear many times in the xml, it only appears once in the xsd.

这里是示例 xsd 和 xml - 这次用 xerces 测试！:

Here is example xsd and xml - tested with xerces this time!:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="productinfo">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="informationset" type="supertype" minOccurs="2" maxOccurs="2"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:complexType name="supertype">
  </xs:complexType>

  <xs:complexType name="Manufacturer">
    <xs:complexContent>
      <xs:extension base="supertype">
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

  <xs:complexType name="Ingredients">
    <xs:complexContent>
      <xs:extension base="supertype">
      </xs:extension>
    </xs:complexContent>
  </xs:complexType>

</xs:schema>

<productinfo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <informationset xsi:type="Manufacturer"></informationset>
  <informationset xsi:type="Ingredients"></informationset>
</productinfo>

注意:您无法控制不同类型的顺序，或者每种类型出现的次数(每种都可以出现一次、多次或根本不出现)——就像java 或 C# 中的多态类列表.但是您至少可以指定整个列表的确切长度(如果您愿意).

NOTE: You can't control the order of the different types, or how many times each type occurs (each could appear once, many times, or not appear at all) - just as with a list of polymorphic classes in java or C#. But you can at least specify at exact length of the list overall (if you like).

例如，我将上面的示例限制为恰好两个元素，但没有设置顺序(即 Manufacturer 可以是第一个，或者 Ingredients 可以是第一个);并且未设置重复次数(即它们可以都是 Manufacturer，或者都是 Ingredients，或者两者之一).

For example, I've restricted the above example to exactly two elements, but the order is not set (i.e. Manufacturer could be first, or Ingredients could be first); and number of repetitions is not set (i.e. they could both be Manufacturer, or both Ingredients, or one of each).

您可以使用 XML Schema type，如下所示:

You can, with XML Schema type, as in:

<productinfo xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <informationset xsi:type="Manufacturer"></informationset>
  <informationset xsi:type="Ingredients"></informationset>
</productinfo>

XSD 为每个定义了单独的复杂类型:

And the XSD defines separate complex types for each one:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
  <xs:element name="productinfo">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="informationset" type="Manufacturer"/>
        <xs:element name="informationset" type="Ingredients"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:complexType name="Manufacturer">
  </xs:complexType>
  <xs:complexType name="Ingredients">
  </xs:complexType>
</xs:schema>

这是xsi:type 的特殊情况.一般来说，不要认为你可以在同名元素中指定属性具有不同的值，因为它们是同一个元素的不同定义.

This is a special case for xsi:type. In general, don't think you can specify attributes to have different values in elements of the same name, because they are different definitions of the same element.

我不是 100% 清楚确切原因——有人知道规范的相关部分吗?

I'm not 100% clear on the precise reason - anyone know the relevant part of the spec?