Using an XML Schema is another method of defining the acceptable tags for an XML document. An XML Schema is written in XML syntax and typically resides in a file separate from the XML document. The XML document must refer to the specific XML Schema document on which it is written.

This sample XML Schema is less focused on an actual implementation and more focused on demonstrating the various ways to write XML data:

• Elements:

                  <xs:element name="FirstName"/>
                  

• Nested Elements:

  		<xs:element name="FormOfPayment">
  		  <xs:complexType>
  		    <xs:sequence>
  		      <xs:element name="ccIssuer"/>
  		      <xs:element ref="ccNumber"/>
  		      <xs:element name="ccExpiration"/>
  		      </xs:sequence>
  		    </xs:complexType>
  		</xs:element>
                  

• Attributes:

  		<xs:element name="PhoneNumber">
  		  <xs:complexType>
  		    <xs:attribute name="countryCode" />
  		    <xs:attribute name="areaCode" />
  		    <xs:attribute name="pNumber"/>
  		  </xs:complexType>
  		</xs:element>
                  

An XML Schema document must have a namespace declaration. For example:

<xs:schema  xmlns:xs="http://www.w3.org/2001/XMLSchema">

For More Information
See the TPF XML User's Guide for the following:

• A list of books and Web sites for learning about writing XML documents
• More information about well-formed and valid XML documents.