The Purchase Order (po.xml) 
---------------------------

<?xml version="1.0"?>
          <purchaseOrder orderDate="1999-10-20">
              <shipTo country="US">
                  <name>Alice Smith</name>
                  <street>123 Maple Street</street>
                  <city>Mill Valley</city>
                  <state>CA</state>
                  <zip>90952</zip>
              </shipTo>
              <billTo country="US">
                  <name>Robert Smith</name>
                  <street>8 Oak Avenue</street>
                  <city>Old Town</city>
                  <state>PA</state>
                  <zip>95819</zip>
              </billTo>
              <comment>Hurry, my lawn is going wild!</comment>
              <items>
                  <item partNum="872-AA">
                      <productName>Lawnmower</productName>
                      <quantity>1</quantity>
                      <USPrice>148.95</USPrice>
                      <comment>Confirm this is electric</comment>
                  </item>
                  <item partNum="926-AA">
                      <productName>Baby Monitor</productName>
                      <quantity>1</quantity>
                      <USPrice>39.98</USPrice>
                      <shipDate>1999-05-21</shipDate>
                  </item>
              </items>
          </purchaseOrder>




































The Purchase Order Schema (po.xsd)
----------------------------------

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

           <xsd:annotation>
            <xsd:documentation xml:lang="en">
             Purchase order schema for Example.com.
             Copyright 2000 Example.com. All rights reserved.
            </xsd:documentation>
           </xsd:annotation>

           <xsd:element name="purchaseOrder" type="PurchaseOrderType"/>

           <xsd:element name="comment" type="xsd:string"/>

           <xsd:complexType name="PurchaseOrderType">
            <xsd:sequence>
             <xsd:element name="shipTo" type="USAddress"/>
             <xsd:element name="billTo" type="USAddress"/>
             <xsd:element ref="comment" minOccurs="0"/>
             <xsd:element name="items"  type="Items"/>
            </xsd:sequence>
            <xsd:attribute name="orderDate" type="xsd:date"/>
           </xsd:complexType>

           <xsd:complexType name="USAddress">
            <xsd:sequence>
             <xsd:element name="name"   type="xsd:string"/>
             <xsd:element name="street" type="xsd:string"/>
             <xsd:element name="city"   type="xsd:string"/>
             <xsd:element name="state"  type="xsd:string"/>
             <xsd:element name="zip"    type="xsd:decimal"/>
            </xsd:sequence>
            <xsd:attribute name="country" type="xsd:NMTOKEN"
               fixed="US"/>
           </xsd:complexType>

           <xsd:complexType name="Items">
            <xsd:sequence>
             <xsd:element name="item" minOccurs="0" maxOccurs="unbounded">
              <xsd:complexType>
               <xsd:sequence>
                <xsd:element name="productName" type="xsd:string"/>
                <xsd:element name="quantity">
                 <xsd:simpleType>
                  <xsd:restriction base="xsd:positiveInteger">
                   <xsd:maxExclusive value="100"/>
                  </xsd:restriction>
                 </xsd:simpleType>
                </xsd:element>
                <xsd:element name="USPrice"  type="xsd:decimal"/>
                <xsd:element ref="comment"   minOccurs="0"/>
                <xsd:element name="shipDate" type="xsd:date" minOccurs="0"/>
               </xsd:sequence>
               <xsd:attribute name="partNum" type="SKU" use="required"/>
              </xsd:complexType>
             </xsd:element>
            </xsd:sequence>
           </xsd:complexType>

           <!-- Stock Keeping Unit, a code for identifying products -->
           <xsd:simpleType name="SKU">
            <xsd:restriction base="xsd:string">
             <xsd:pattern value="\d{3}-[A-Z]{2}"/>
            </xsd:restriction>
           </xsd:simpleType>

          </xsd:schema>