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 that is separate from the XML document. The XML document must refer to the specific XML Schema document on which it is written.

Paul decides to create an XML Schema that coincides with the DTD for a PNR that he wrote previously. He knows that the organization of data in an XML document is the key to its success. However, Paul is less focused on an actual implementation of this XML Schema 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>
                  

When he has written the XML Schema document, Paul ensures that he has included the following namespace declaration:

<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 XML Schema and its syntax
• More information about XML Schema, namespaces, and specifying the encoding of your documents on the TPF 4.1 system.