Table of contents

Appendices

2.4 Anonymous Type Definitions

Schemas can be constructed by defining sets of named types such as PurchaseOrderType and then declaring elements such as purchaseOrder that reference the types using the type= construction. This style of schema construction is straightforward but it can be unwieldy, especially if you define many types that are referenced only once and contain very few constraints. In these cases, a type can be more succinctly defined as an anonymous type which saves the overhead of having to be named and explicitly referenced.

The definition of the type Items in po.xsd contains two element declarations that use anonymous types (item and quantity). In general, you can identify anonymous types by the lack of a type= in an element (or attribute) declaration, and by the presence of an un-named (simple or complex) type definition:

NOTE: 

Two Anonymous Type Definitions

<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>

In the case of the item element, it has an anonymous complex type consisting of the elements productName, quantity, USPrice, comment, and shipDate, and an attribute called partNum. In the case of the quantity element, it has an anonymous simple type derived from integer positiveInteger whose value ranges between 1 and 99.