XSD <any> Element

The <any> element enables us to extend the XML document with elements not specified by the schema!

The <any> element

The <any> element enables us to extend the XML document with elements not specified by the schema!

This example is a fragment referenced from an XML schema named "family.xsd". It demonstrates a declaration for the "person" element. By using the <any> element, we can extend the content of "person" through any element (after <lastname>):

<xs:element name="person">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="firstname" type="xs:string"/>
      <xs:element name="lastname" type="xs:string"/>
      <xs:any minOccurs="0"/>
    </xs:sequence>
  </xs:complexType>
</xs:element>

Now, we want to use the "children" element to extend the "person" element. In this case, we can do so even if the author of the above schema has not declared any "children" element.

Please see this schema file, named "children.xsd":

<?xml version="1.0" encoding="ISO-8859-1"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="http://www.codew3c.com"
xmlns="http://www.codew3c.com"
elementFormDefault="qualified">
<xs:element name="children">
  <xs:complexType>
    <xs:sequence>
      <xs:element name="childname" type="xs:string"
      maxOccurs="unbounded"/>
    </xs:sequence>
  </xs:complexType>
</xs:element>
</xs:schema>

This XML file (named "Myfamily.xml") uses components from two different schemas, "family.xsd" and "children.xsd":

<?xml version="1.0" encoding="ISO-8859-1"?>
<persons xmlns="http://www.microsoft.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:SchemaLocation="http://www.microsoft.com family.xsd
http://www.codew3c.com children.xsd">
<person>
<firstname>David</firstname>
<lastname>Smith</lastname>
<children>
  <childname>mike</childname>
</children>
</person>
<person>
<firstname>Tony</firstname>
<lastname>Smith</lastname>
</person>
</persons>

The above XML file is valid because the schema "family.xsd" allows us to extend the "person" element by adding an optional element after the "lastname" element.

<any> and <anyAttribute> can both be used to create extensible documents! They enable documents to include additional elements that are not declared in the main XML schema.