<xs:schema
   xmlns:xs="http://www.w3.org/2001/XMLSchema"
   xmlns:po="http://openuri.org/easypo"
   targetNamespace="http://openuri.org/easypo"
   elementFormDefault="qualified">

  <xs:element name="purchase-order">
    <xs:complexType>
      <xs:sequence>
        <xs:element name="customer" type="po:customer"/>
        <xs:element name="date" type="xs:dateTime"/>
        <xs:element name="line-item" type="po:line-item" minOccurs="0" maxOccurs="unbounded"/>
        <xs:element name="shipper" type="po:shipper" minOccurs="0" maxOccurs="1"/>
      </xs:sequence>
    </xs:complexType>
  </xs:element>

  <xs:complexType name="customer">
    <xs:sequence>
      <xs:element name="name" type="xs:string"/>
      <xs:element name="address" type="xs:string"/>
    </xs:sequence>
    <xs:attribute name="age" type="xs:int"/>
  </xs:complexType>

  <xs:complexType name="line-item">
    <xs:sequence>
      <xs:element name="description" type="xs:string"/>
      <xs:element name="per-unit-ounces" type="xs:decimal"/>
      <xs:element name="price" type="xs:decimal"/>
      <xs:element name="quantity" type="xs:integer"/>
    </xs:sequence>
  </xs:complexType>

  <xs:complexType name="shipper">
    <xs:sequence>
      <xs:element name="name" type="xs:string"/>
      <xs:element name="per-ounce-rate" type="xs:decimal"/>
    </xs:sequence>
  </xs:complexType>

</xs:schema>