定义一个必须为空且没有属性的 XML 元素
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Define an XML element that must be empty and has no attributes
提问by John S
I needed to define an XML element that has no sub-elements or any content at all, and has no attributes.
我需要定义一个完全没有子元素或任何内容并且没有属性的 XML 元素。
This is what I am doing:
这就是我正在做的：
<xs:element name="myEmptyElement" type="_Empty"/>
<xs:complexType name="_Empty">
</xs:complexType>
This appears to work fine, but I have to wonder if there is a way to do this without having to declare a complex type. Also, if there is anything wrong with what I have, please let me know.
这似乎工作正常，但我想知道是否有办法在不必声明复杂类型的情况下做到这一点。另外，如果我所拥有的有任何问题，请告诉我。
Anticipating that someone might be curious why I would need such an element: It is for a SOAP operation that does not require any parameter values.
预计有人可能会好奇我为什么需要这样一个元素：它用于不需要任何参数值的 SOAP 操作。
回答by kjhughes
(1) You could avoid defining a named xs:complexType:
(1) 你可以避免定义一个命名的xs:complexType：
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="myEmptyElement">
<xs:complexType/>
</xs:element>
</xs:schema>
(2) You could use a xs:simpleTypeinstead of a xs:complexType:
(2) 您可以使用 axs:simpleType代替 a xs:complexType：
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="myEmptyElement">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:maxLength value="0"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
</xs:schema>
(3) You could use fixed=""[credit: @Nemo]:
(3) 你可以使用fixed=""[credit: @Nemo]:
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="myEmptyElement" type="xs:string" fixed=""/>
</xs:schema>
(4) But note that if you avoid saying anything about the content model:
(4) 但请注意，如果您避免提及内容模型：
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:element name="myEmptyElement"/>
</xs:schema>
You'll be allowing any attributes on and any content in myEmptyElement.
您将允许myEmptyElement.
回答by Emidio Stani
Another example could be:
另一个例子可能是：
<xs:complexType name="empty">
<xs:sequence/>
</xs:complexType>
<xs:element name="myEmptyElement" type="empty>
or
或者
<xs:element name="myEmptyElement">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value=""/>
</xs:restriction>
</xs:simpleType>
</xs:element>
or
或者
<xs:element name="myEmptyElement">
<xs:complexType>
<xs:complexContent>
<xs:restriction base="xs:anyType"/>
</xs:complexContent>
</xs:complexType>
</xs:element>
