test/schemas/item_1.xsd

<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:element name="comment" type="xsd:string"/>
<!-- 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: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>
<!-- attributeGroup replaces individual declarations -->
      <xsd:attributeGroup ref="ItemDelivery"/>
    </xsd:complexType>
  </xsd:element>
  <xsd:attributeGroup name="ItemDelivery">
    <xsd:attribute name="partNum" type="SKU" use="required"/>
    <xsd:attribute name="weightKg" type="xsd:decimal"/>
    <xsd:attribute name="shipBy">
      <xsd:simpleType>
        <xsd:restriction base="xsd:string">
          <xsd:enumeration value="air"/>
          <xsd:enumeration value="land"/>
          <xsd:enumeration value="any"/>
        </xsd:restriction>
      </xsd:simpleType>
    </xsd:attribute>
  </xsd:attributeGroup>
</xsd:schema>