Creating a user-defined filter follows the same pattern as creating a user-defined client. You must create a derived body class, where you specify the rules for filtering. If your filter’s body class has any new public members (in addition to those inherited from its base classes), you must also create a corresponding derived handle class. The predefined Trace Level filter was created in the same way that you would create your own filter, so the source code for RWTraceLevelFilter and RWTraceLevelFilterImp is an example.