XSD The <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.
The following example is a fragment from an XML schema called "family.xsd". It shows a declaration for the "person" element. By using the <any> element we can extend (after <lastname>) the content of "person" with any element:
<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 extend the "person" element with a "children" element. In this case we can do so, even if the author of the schema above never declared any "children" element.
Look at this schema file, called "children.xsd":
<?xml version="1.0" encoding="UTF-8"?>
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
targetNamespace="https://www.w3schools.com"
xmlns="https://www.w3schools.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>
The XML file below (called "Myfamily.xml"), uses components from two different schemas; "family.xsd" and "children.xsd":
<?xml version="1.0" encoding="UTF-8"?>
<persons xmlns="http://www.microsoft.com"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.microsoft.com family.xsd
https://www.w3schools.com children.xsd">
<person>
<firstname>Hege</firstname>
<lastname>Refsnes</lastname>
<children>
<childname>Cecilie</childname>
</children>
</person>
<person>
<firstname>Stale</firstname>
<lastname>Refsnes</lastname>
</person>
</persons>
The XML file above is valid because the schema "family.xsd" allows us to extend the "person" element with an optional element after the "lastname" element.
The <any> and <anyAttribute> elements are used to make EXTENSIBLE documents! They allow documents to contain additional elements that are not declared in the main XML schema.