Re: [hibernate-dev] Concept of "service availability"

I had a similar problem before: In an osgi project we needed the ability to extend a main system with functionality provided in addon bundles We developed a main system which could be extended and complemented with extenders of several kinds. The main system provided (exported) a tree of marker interfaces like public interface ExtenderMarker {}; public interface TypeAExtender extends ExtenderMarker public interface TypeBExtender extends ExtenderMarker .... and had a "helper" which scans services, tracks services and initially scans the framework for interesting services (started from the bundle activator of the main system). The extender bundles only implemented the extenders and registered OSGI services with the ExtenderMarker interface and maybe also the concrete interface. They had no more tasks to do. Now the main system could "use" the extenders which got registered by the "helper" and the "helper" was handling the live cycle events, etc. Simple approach based on the whiteboard pattern. - Martin