Example: Filtering based on groups

This section is non-normative.

In this scenario, groups are used for filtering within a conditional processing attribute.

The following code sample illustrates a list item that applies to two different types of product. It applies to one application server and two database applications:

<ol>
  <li>Common step</li>
  <li product="appServer(mySERVER) database(dbOne dbOther)">
    <ph>Do something special for databases dbTwo or dbOther when installing on mySERVER</ph>
  </li>
  <!-- additional list items -->
</ol>

If a publisher decides to exclude the application server mySERVER, then the appServer() group evaluates to exclude. This can be done by setting product="mySERVER" to exclude or by setting appServer="mySERVER" to exclude. This means the item is excluded, regardless of how the values dbOne or dbOther evaluate. If a rule is specified for both product="mySERVER" and appServer="mySERVER", the rule for the more specific group name "appServer" takes precedence.

Similarly, if both dbOne and dbOther evaluate to exclude, then the database() group evaluates to exclude and the element is excluded regardless of how the "mySERVER" value is set.

In more advanced usage, a DITAVAL can be used to specify a rule for a group name. For example, an author could create a DITAVAL rule that sets product="database" to "exclude". This is equivalent to setting a default of "exclude" for any individual value in a database() group; it also excludes the more common usage of "database" as a single value within the @product attribute. Thus when "myDB" appears in a database() group within the @product attribute, the full precedence for determining whether to include or exclude the value is as follows:

Check for a DITAVAL rule for database="dbOne"
Check for a DITAVAL rule for product="dbOne"
Check for a DITAVAL rule for product="database" (default for the database group)
Check for a DITAVAL rule for "product" (default for the @product attribute)
Check for a default rule for all conditions (default of include or exclude for all attributes)
Otherwise, evaluate to "include"