Not all Java source files or Javadocs exist for the Runtime Interface Definition Library.
ridl.jar is built from a combination of Java source files and class files
generated from IDL files during a complete build of Apache OpenOffice.
The IDL documentation can be found here:
http://www.openoffice.org/api/docs/common/ref/com/sun/star/module-ix.html
Available Java sources and generated Javadocs are included in their respective jars.