What is a Complex Element

什么是复合元素（Complex Elements）？

A complex element is an XML element that contains other elements and/or attributes.
复合元素（Complex Elements）是含有其他元素和/或属性的XML元素

There are four kinds of complex elements:
有四种复合元素（Complex Elements）：

• empty elements
  空元素
• elements that contain only other elements
  只含有其他元素的元素
• elements that contain only text
  只含有文本的元素
• elements that contain both other elements and text
  含有文本和其他元素的元素

Note: Each of these elements may contain attributes as well!
注意：这些元素中的每一个也许还含有属性!

---

Examples of Complex Elements
复合元素（Complex Elements）的例子

A complex XML element, "product", which is empty:
一个空的复合XML元素"product"：

<product pid="1345"/>

A complex XML element, "employee", which contains only other elements:
只含有其他元素的复合XML元素, "employee"

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

A complex XML element, "food", which contains only text:
只含有文本的复合XML元素， "food"：

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

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

<description>

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

---

How to Define a Complex Element
怎样定义一个复合元素（Complex Elements）？

Look at this complex XML element, "employee", which contains only other elements:
看这个只含有其他元素的复合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:
我们有两种方法可以在一篇XML Schema里定义一个复合元素（Complex Elements）：

1. The "employee" element can be declared directly by naming the element, like this:
1. "employee"元素可以直接通过命名元素的方式被声明，像这样：

<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.
如果你用了上面的方法，那么只有"employee"元素才可以用指定的复合类型。注意子元 素"firstname" 和 "lastname",它们是被包围在<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XSD指示器 这章里你可以学到关于指示器更多内容。

2. The "employee" element can have a type attribute that refers to the name of the complex type to use:
2. "employee"元素可以有个类型属性，其所指的是要用的复合类型的名称

<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:
如果你用上述方法，几个元素指的可以是相同的复合类型，就像这样：

<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:
你也可以在现存的复合元素（Complex Elements）上再加上一个复合元素（Complex Elements），并添加一些元素，就像这样：

<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 Complex 空元素
w3pop.com / 2006-09-21

XSD Complex 元素 XSD 复合类型 - 纯元素

An empty complex element cannot have contents, only attributes.
一个空的复合元素不能含有内容，只能含有属性。

---

Complex Empty Elements
复合空元素（Complex Empty Elements）

An empty XML element:
一个空的XML元素：

<product prodid="1345" />

The "product" element above has no content at all. To define a type with no content, we must define a type that allows only elements in its content, but we do not actually declare any elements, like this:
上述"product"元素完全不含内容。为定义不含内容的类型，我们必须定义一个内容中只允许出现元素的类型，但我们不需要声明任何元素，就像这样：

<xs:element name="product">

  <xs:complexType>
    <xs:complexContent>
      <xs:restriction base="xs:integer">
        <xs:attribute name="prodid" type="xs:positiveInteger"/>

      </xs:restriction>
    </xs:complexContent>
  </xs:complexType>
</xs:element>

In the example above, we define a complex type with a complex content. The complexContent element signals that we intend to restrict or extend the content model of a complex type, and the restriction of integer declares one attribute but does not introduce any element content.
上述例子中，我们定义了一个有复合内容的复合类型。复合内容的元素表示了我们想要约束或扩充的复合类型的内容模式。对整数的约束声明了一个属性，但并没有介绍任何元素内容。

However, it is possible to declare the "product" element more compactly, like this:
但是，可以更加简洁地声明"product"元素，就像这样：

<xs:element name="product">
  <xs:complexType>

    <xs:attribute name="prodid" type="xs:positiveInteger"/>
  </xs:complexType>
</xs:element>

Or you can give the complexType element a name, and let the "product" element have a type attribute that refers to the name of the complexType (if you use this method, several elements can refer to the same complex type):
或者你可以给complexType元素起个名称，并让"product"元素有个类型属性，而且类型属性引用的是complexType的名称（如果你用这个方法，几个元素可以引用相同的复合类型）：

<xs:element name="product" type="prodtype"/>

<xs:complexType name="prodtype">
  <xs:attribute name="prodid" type="xs:positiveInteger"/>
</xs:complexType>

XSD 复合类型 - 纯元素
w3pop.com / 2006-09-21

XSD Complex 空元素 XSD 复合文字 - 纯元素

An "elements-only" complex type contains an element that contains only other elements.
“只有元素（Elements-only）”复合类型含有一个只包含其他元素的元素

---

Complex Types Containing Elements Only
复合类型只含有元素

An XML element, "person", that contains only other elements:
一个XML元素, "person",只含有其他元素：

<person>
<firstname>John</firstname>
<lastname>Smith</lastname>
</person>

You can define the "person" element in a schema, like this:
你可以在一篇schema里定义"person"元素，就像这样

<xs:element name="person">
  <xs:complexType>

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

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

Notice the <xs:sequence> tag. It means that the elements defined ("firstname" and "lastname") must appear in that order inside a "person" element.
注意<xs:sequence>标签。这表示所定义的元素("firstname" 和 "lastname")必须在"person"元素里以那样的次序出现。

Or you can give the complexType element a name, and let the "person" element have a type attribute that refers to the name of the complexType (if you use this method, several elements can refer to the same complex type):
或者你可以给complexType元素取个名字，让"person"元素有个类型属性，这个类型属性的名字可以参考使用complexType元素的名字（如果你用这个方法，几个元素可以同时参考使用相同的复合类型）。

<xs:element name="person" type="persontype"/>

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

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

XSD 复合文字 - 纯元素
w3pop.com / 2006-09-21

XSD 复合类型 - 纯元素 XSD 混合内容的复合类型

A complex text-only element can contain text and attributes.
一个复合只含文本元素（Complex Text-Only Elements）可以含有文本和属性。

---

Complex Text-Only Elements
复合只含文本元素（Complex Text-Only Elements）

This type contains only simple content (text and attributes), therefore we add a simpleContent element around the content. When using simple content, you must define an extension OR a restriction within the simpleContent element, like this:
这种类型只含有简单内容（文本和属性），因此我们在内容周围添加一个simpleContent元素，当用到简单内容时，你必须在simpleContent元素里定义一个扩展或约束，就像这样：

<xs:element name="somename">

  <xs:complexType>
    <xs:simpleContent>
      <xs:extension base="basetype">
        ....
        ....
      </xs:extension>     
    </xs:simpleContent>
  </xs:complexType>

</xs:element>

OR

<xs:element name="somename">
  <xs:complexType>
    <xs:simpleContent>
      <xs:restriction base="basetype">

        ....
        ....
      </xs:restriction>     
    </xs:simpleContent>
  </xs:complexType>
</xs:element>

Tip: Use the extension/restriction element to expand or to limit the base simple type for the element.
提示：用extension/restriction元素扩展或限制元素的基本简单类型（base simple type）。

Here is an example of an XML element, "shoesize", that contains text-only:
这儿是只含有文本的一个XML元素, "shoesize"：

<shoesize country="france">35</shoesize>

The following example declares a complexType, "shoesize". The content is defined as an integer value, and the "shoesize" element also contains an attribute named "country":
下面的例子声明了一个复合类型，"shoesize"元素。内容定义为整数值，"shoesize"元件含有名为"country"的属性。

<xs:element name="shoesize">
  <xs:complexType>
    <xs:simpleContent>
      <xs:extension base="xs:integer">
        <xs:attribute name="country" type="xs:string" />

      </xs:extension>
    </xs:simpleContent>
  </xs:complexType>
</xs:element>

We could also give the complexType element a name, and let the "shoesize" element have a type attribute that refers to the name of the complexType (if you use this method, several elements can refer to the same complex type):
我们可以给complexType元件起个名字，让"shoesize"元件有种类属性，种类属性的名字就是complexType元件的名字。（如果你用这种方法，几个元素指的可以是相同的复合类型）

<xs:element name="shoesize" type="shoetype"/>

<xs:complexType name="shoetype">

  <xs:simpleContent>
    <xs:extension base="xs:integer">
      <xs:attribute name="country" type="xs:string" />
    </xs:extension>

  </xs:simpleContent>
</xs:complexType>

XSD 混合内容的复合类型
w3pop.com / 2006-09-21

XSD 复合文字 - 纯元素 XSD 指示器复合类型

A mixed complex type element can contain attributes, elements, and text.
混合内容的复合类型元素（XSD Complex Types Element With Mixed Content ）可以含有属性，元素，和文本。

---

Complex Types with Mixed Content
混合内容的复合类型

An XML element, "letter", that contains both text and other elements:
一个XML元素，"letter",既含有文本又含有其他元素：

<letter>
Dear Mr.<name>John Smith</name>.
Your order <orderid>1032</orderid>
will be shipped on <shipdate>2001-07-13</shipdate>.

</letter>

The following schema declares the "letter" element:
下面的XML公式声明了"letter"元素：

<xs:element name="letter">
  <xs:complexType mixed="true">
    <xs:sequence>
      <xs:element name="name" type="xs:string"/>

      <xs:element name="orderid" type="xs:positiveInteger"/>
      <xs:element name="shipdate" type="xs:date"/>
    </xs:sequence>

  </xs:complexType>
</xs:element>

Note: To enable character data to appear between the child-elements of "letter", the mixed attribute must be set to "true". The <xs:sequence> tag means that the elements defined (name, orderid and shipdate) must appear in that order inside a "letter" element.
注意：为了使字符数据能出现在"letter"子元件之间，mixed属性必须设置为"true"。<xs:sequence>标签指出了已定义的元素(name, orderid 和shipdate)在"letter"元素里必须以指定的顺序出现

We could also give the complexType element a name, and let the "letter" element have a type attribute that refers to the name of the complexType (if you use this method, several elements can refer to the same complex type):
我们可以给这个complexType元素一个名称，并且让"letter"元素有一个引用了complexType的名称的种类属性（如果你用了这个方法，几个元素可以同时使用相同的复合类型）：

<xs:element name="letter" type="lettertype"/>

<xs:complexType name="lettertype" mixed="true">
  <xs:sequence>
    <xs:element name="name" type="xs:string"/>

    <xs:element name="orderid" type="xs:positiveInteger"/>
    <xs:element name="shipdate" type="xs:date"/>
  </xs:sequence>

</xs:complexType>