Do you have an example, I'm not sure to understand. Are you talking about a SU that depends on another SU ?
Well, elements in a SU can have dependencies on both component libraries and normal java libraries. SAs may contain SUs that have dependencies upon different versions of these libraries.
The classic example is during an ongoing business migration scenario. Step one is to roll out an integration solution for the existing legacy system using JBI. Then you build a new solution to replace the existing one and start to roll it out over a period of months to all the locations. Eventually you have upgraded all your sites and you can decommission the legacy system.
In the intervening time, you have new and old systems running in parallel. If the cutover period is long enough, you may be rolling out v1.1 patches to new systems, whilst installing v1.0 code elsewhere and still maintaining legacy code.
If ServiceMix is forming the integration layer then you will want to be able to deploy SUs for new solutions that can use later versions of dependent libraries without having any impact on previously implemented solutions on earlier dependencies.
It's similar to the issues involved in maintaining XML Schema versions for interface specifications.
Terry
