Hi Charlie, thanks for your input. We have a very basic prototype which provides Validator and ValidatorFactory as OSGi services. As you say that's a first step, but its getting more complex when taking XML based mappings, message bundles and so on into account. Generally whenever we load any classes by name (as we e.g. do for XML-declared constraints) we need to be sure to do so using the "right" classloader. I've some ideas around this and got also some stuff working; Atm. it's mainly a time/resource question of bringing this into a state where its actually usable and releasable. So any help to this is highly welcome.