<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>