XML in a Nutshell, 3rd Edition

Defining New Simple Types

To show how new simple types can be defined, let’s extend the phone element from the example application to support a new attribute called location. This attribute will be used to differentiate between work and home phone numbers. This attribute will have a new simple type called locationType, which will be referenced from the contactsType definition:

<xs:complexType name="contactsType">
  <xs:sequence>
    <xs:element name="phone" minOccurs="0">
      <xs:complexType>
        <xs:attribute name="number" type="xs:string"/>
         <xs:attribute name="location" type="addr:locationType"/>
      </xs:complexType>
    </xs:element>
  </xs:sequence>
</xs:complexType>
     
<xs:simpleType name="locationType">
  <xs:restriction base="xs:string"/>
</xs:simpleType>

Of course, a location type that just maps to the built-in xs:string type isn’t particularly useful. Fortunately, schemas can strictly control the possible values of simple types through a mechanism called facets.