A complex element contains other elements and/or attributes.
一个复合元素包含其它元素和 / 或属性。

What is a Complex Element?
什么是复合元素？

A complex element is an XML element that contains other elements and/or attributes.
复合元素是包含其它元素和 / 或属性的XML元素：

There are four kinds of complex elements:
下面列举四种复合元素：

• empty elements
  空元素
• elements that contain only other elements
  只包含其它元素的元素
• elements that contain only text
  只包含文本的元素
• elements that contain both other elements and text
  包含文本和其它元素的元素

Note: Each of these elements may contain attributes as well!
注意：上述每个元素中可能还包含属性！

Examples of Complex Elements
复合元素案例

A complex XML element, "product", which is empty:
下面列举了一个空复合XML元素“product”：

<product pid="1345"/>

A complex XML element, "employee", which contains only other elements:
只包含其它元素的复合XML元素“employee”：

<employee>
<firstname>John</firstname>
<lastname>Smith</lastname>
</employee>

A complex XML element, "food", which contains only text:
只包含文本的复合XML元素"food"：

<food type="dessert">Ice cream</food>

A complex XML element, "description", which contains both elements and text:
包含元素和文本的复合XML元素"description"：

<description>

It happened on <date lang="norwegian">03.03.99</date> ....
</description>

How to Define a Complex Element
复合元素的定义方法

Look at this complex XML element, "employee", which contains only other elements:
先请看看下面这个只包含其它元素的复合XML元素"employee"：

<employee>
<firstname>John</firstname>
<lastname>Smith</lastname>

</employee>

We can define a complex element in an XML Schema two different ways:
我们可以使用两种不同的方法在一份XML Schema文档里定义一个复合元素：

1. The "employee" element can be declared directly by naming the element, like this:
1. "employee"元素可以直接通过为元素命名的方式被声明，如下所示：

<xs:element name="employee">
 <xs:complexType>
 <xs:sequence>
 <xs:element name="firstname" type="xs:string"/>

 <xs:element name="lastname" type="xs:string"/>
 </xs:sequence>
 </xs:complexType>
</xs:element>

If you use the method described above, only the "employee" element can use the specified complex type. Note that the child elements, "firstname" and "lastname", are surrounded by the <sequence> indicator. This means that the child elements must appear in the same order as they are declared. You will learn more about indicators in the XSD Indicators chapter.
如果你用了上述方法，那么只有"employee"元素才可以使用指定的复合类型。注意：子元素"firstname" 和 "lastname"是被包围在“<sequence>指示器”元素里的。这意味着，子元素必须以它们被声明的顺序出现。在讲述XSD指示器的章节中，你可以学到关于指示器更多知识。

2. The "employee" element can have a type attribute that refers to the name of the complex type to use:
2. "employee"元素可以包含一个类型属性，用于指定需要使用的复合类型名称：

<xs:element name="employee" type="personinfo"/>

<xs:complexType name="personinfo">

 <xs:sequence>
 <xs:element name="firstname" type="xs:string"/>
 <xs:element name="lastname" type="xs:string"/>

 </xs:sequence>
</xs:complexType>

If you use the method described above, several elements can refer to the same complex type, like this:
如果你使用上述方法，几个元素可以引用相同的复合类型，如下所示：

<xs:element name="employee" type="personinfo"/>
<xs:element name="student" type="personinfo"/>
<xs:element name="member" type="personinfo"/>

<xs:complexType name="personinfo">
 <xs:sequence>
 <xs:element name="firstname" type="xs:string"/>
 <xs:element name="lastname" type="xs:string"/>

 </xs:sequence>
</xs:complexType>

You can also base a complex element on an existing complex element and add some elements, like this:
你也可以在现有的复合元素的基础上再加上一个复合元素，并添加一些其它元素，如下所示：

<xs:element name="employee" type="fullpersoninfo"/>

<xs:complexType name="personinfo">
 <xs:sequence>
 <xs:element name="firstname" type="xs:string"/>

 <xs:element name="lastname" type="xs:string"/>
 </xs:sequence>
</xs:complexType>

<xs:complexType name="fullpersoninfo">

 <xs:complexContent>
 <xs:extension base="personinfo">
 <xs:sequence>
 <xs:element name="address" type="xs:string"/>

 <xs:element name="city" type="xs:string"/>
 <xs:element name="country" type="xs:string"/>
 </xs:sequence>

 </xs:extension>
 </xs:complexContent>
</xs:complexType>

XSD 约束面 XSD 复合空元素

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