A repository item type can have subtypes that include additional properties that are not part of the base item type. This feature is commonly used in the Oracle ATG Web Commerce catalog for the SKU item type. A SKU subtype might add properties that are specific to certain SKUs but which are not relevant for other SKUs.

When you list properties to index, you can use the subtype attribute of the property element to specify properties that are unique to a specific item subtype. For example, suppose you have a furniture-sku subtype that adds properties specific to furniture SKUs. You might specify your SKU properties like this:

<item property-name="childSKUs">
  <text-properties>
    <property name="description"/>
    <property name="color"/>
    <property name="woodType" subtype="furniture-sku"/>
  </text-properties>
</item>

This specifies that the description and color properties should be included in the XHTML output for all SKUs, but for SKUs whose subtype is furniture-sku, the woodType property should also be included.

The item element also has a subtype attribute for specifying a subtype-specific property whose value is a repository item. If woodType is a repository item, the example above would look something like this:

<item property-name="childSKUs">
  <text-properties>
    <property name="description"/>
    <property name="color"/>
  </text-properties>
  <item property-name="woodType" subtype="furniture-sku"/>
    <text-properties>
      <property name="hardness"/>
      <property name="stainType"/>
    </text-properties>
  </item>
</item>