The JDK 1.4 logging framework addons package is near the middle of the java layered frameworks shown in the Architectural Layer Diagram. Its main purpose is to extend the core JDK 1.4 logging framework package (java.util.logging) with useful things provided by the JLF proprietary logging framework but missing from the JDK framework. This add-on package brings a lot of the good things from the proprietary JLF logging framework for use in the new standard framework, plus instruments errors and events in conjunction with the Vital Sign framework.
See the Logging Framework Add-on Class Diagram for the major classes and methods involved in the framework. The key classes are AppError and AppInstrument. The source code for the framework begins here. Here is the JavaDoc for all of JLF, including the configuration framework.