XML Schema restriction element
Definition and usage
The restriction element defines constraints for simpleType, simpleContent, or complexContent.
Element information
| Occurrence times | Once |
| Parent element | complexContent |
| Content | group, all, choice, sequence, attribute, attributeGroup, anyAttribute |
Grammar
<restriction id=ID base=QName any attributes > Content for simpleType: (annotation?,(simpleType?,(minExclusive|minInclusive| maxExclusive|maxInclusive|totalDigits|fractionDigits| length|minLength|maxLength|enumeration|whiteSpace|pattern)*)) Content for simpleContent: (annotation?,(simpleType?,(minExclusive |minInclusive| maxExclusive|maxInclusive|totalDigits|fractionDigits| (length|minLength|maxLength|enumeration|whiteSpace|pattern)*)?, ((attribute|attributeGroup)*,anyAttribute?) Content for complexContent: (annotation?,(group|all|choice|sequence)?, ((attribute|attributeGroup)*,anyAttribute?) </restriction>
(The symbol declaration is in the restriction element, which can appear zero or one times.)
| Attribute | Description |
|---|---|
| id | Optional. Specifies a unique ID for the element. |
| base | Required. Specifies the name of the built-in data type, simpleType, or complexType elements defined in the schema (or any other schema indicated by the specified namespace). |
| any attributes | Optional. Specifies any other attributes with non-schema namespaces. |
Instance
Example 1
The following example defines an element named "age" with constraints. The value of age cannot be less than 0 or greater than 100:
<xs:element name="age">
<xs:simpleType>
<xs:restriction base="xs:integer">
<xs:minInclusive value="0"/>
<xs:maxInclusive value="100"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
Example 2
This example defines an element named "initials". The "initials" element is a constrained simple type. Acceptable values are three uppercase or lowercase letters from a to z:
<xs:element name="initials">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:pattern value="[a-zA-Z][a-zA-Z][a-zA-Z]"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
Example 3
This example defines an element named "password". The "password" element is a constrained simple type. The value must be at least 5 characters and at most 8 characters long:
<xs:element name="password">
<xs:simpleType>
<xs:restriction base="xs:string">
<xs:minLength value="5"/>
<xs:maxLength value="8"/>
</xs:restriction>
</xs:simpleType>
</xs:element>
Example 4
This example demonstrates a complex type definition using constraints. The complex type "Chinese_customer" is derived from a common customer complex type, with the fixed value of the country element being "China":
<xs:complexType name="customer">
<xs:sequence>
<xs:element name="firstname" type="xs:string"/>
<xs:element name="lastname" type="xs:string"/>
<xs:element name="country" type="xs:string"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="Chinese_customer">
<xs:complexContent>
<xs:restriction base="customer">
<xs:sequence>
<xs:element name="firstname" type="xs:string"/>
<xs:element name="lastname" type="xs:string"/>
<xs:element name="country" type="xs:string" fixed="China"/>
</xs:sequence>
</xs:restriction>
</xs:complexContent>
</xs:complexType>
