# XML Schema extension Element

Complete XML Schema Reference

## Definition and Usage

The extension element extends an existing simpleType or complexType element.

### Element Information

- Parent elements: simpleContent, complexContent

### Syntax

<extension
id=ID
base=QName
any attributes
>
(annotation?,((group|all|choice|sequence)?,
((attribute|attributeGroup)*,anyAttribute?)))
</extension>

(The ? sign declares that the element can occur zero or one time, and the * sign declares that the element can occur zero or more times inside the extension element)

Attribute | Description
--- | ---
id | Optional. Specifies a unique ID for the element
base | Required. Specifies the name of a built-in data type, a simpleType element, or a complexType element
any attributes | Optional. Specifies any other attributes with non-schema namespace

### Example 1

The following example extends an existing simpleType by adding an attribute:

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:simpleType name="size">
<xs:restriction base="xs:string">
<xs:enumeration value="small" />
<xs:enumeration value="medium" />
<xs:enumeration value="large" />
</xs:restriction>
</xs:simpleType>
<xs:complexType name="jeans">
<xs:simpleContent>
<xs:extension base="size">
<xs:attribute name="sex">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:enumeration value="male" />
<xs:enumeration value="female" />
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:schema>

### Example 2

The following example extends an existing complexType element by adding three elements:

<?xml version="1.0"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema">
<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>
</xs:schema>

Complete XML Schema Reference

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