       <xsd:schema xmlns:xsd="http://www.w3.org/2000/08/XMLSchema">

//        <xsd:annotation>
//         <xsd:documentation>
//          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"
//            use="fixed" value="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"/>
           </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>