Multi-bundle scoping techniques are essential for dividing large systems into loosely-coupled collections of bundles. If you are developing a large application with many bundles, you'll want to manage its complexity using a higher-level scoping mechanism than a single bundle.
For example, multi-bundle applications can be scoped to avoid unwanted interference between the applications. Another example is separating "kernel" bundles from applications supported by the kernel in order to increase the stability of the kernel, similarly to the way applications are separated from an operating system kernel.
This presentation, first given at EclipseCon Europe 2011, explores existing scoping mechanisms: metadata rewriting, composite bundles, framework hooks, and region digraphs.
It then covers scoping in the Subsystems draft OSGi standard for multi-bundle applications.