Modular applications and OSGi are two terms that often go hand in hand in today's enteprirse Java market. But as Oliver Gierke points out, modularity can also be achieved using alternatives like the Hera project. Read Oliver Gierke's post 'Achieving application modularity with Hera': http://www.olivergierke.de/wordpress/2009/05/achieving-application-modularity-with-hera/