Tools like Reflections [1], Scannotaions [2] and many more [3] provide the ability to find instances of annotations on the classpath. They also provide the ability to find subclasses of an interface. This kind of tooling is commonly needed by Java EE. Different tools use different approaches to gather the information, but it is definitely something that could be captured when building a module. At the very least, it is important to ensure that these tools continue to work.
Stephen [1] https://github.com/ronmamo/reflections [2] http://scannotation.sourceforge.net/ [3] http://stackoverflow.com/questions/259140/scanning-java-annotations-at-runtime
