XML Schema union element

XSD Element

Definition and usage

The union element defines a collection of simpleType definitions.

Element information

Occurrence times One
Parent element simpleType
Content annotation, simpleType

Syntax

<union
id=ID
memberTypes="list of QNames"
any attributes
>
(annotation?,(simpleType*))
</union>

(The '?' symbol indicates that the element can occur zero or one times within the union element.)

Attribute Description
id Optional. Specifies a unique ID for the element.
memberTypes Optional. Specifies a list of names of built-in data types or simpleType elements defined in the schema.
any attributes Optional. Specifies any other attributes with a non-schema namespace.

Instance

Example 1

This example is a simple type that merges two simple types:

<xs:element name="jeans_size">
  <xs:simpleType>
    <xs:union memberTypes="sizebyno sizebystring" />
  </xs:simpleType>
</xs:element>
<xs:simpleType name="sizebyno">
  <xs:restriction base="xs:positiveInteger">
    <xs:maxInclusive value="42"/>
  </xs:restriction>
</xs:simpleType>
<xs:simpleType name="sizebystring">
  <xs:restriction base="xs:string">
    <xs:enumeration value="small"/>
    <xs:enumeration value="medium"/>
    <xs:enumeration value="large"/>
  </xs:restriction>
</xs:simpleType>

XSD Element