[lmm]

It would be nice to be able to make rigid and well-defined boundaries without having to add the overhead of serialization and network boundaries.

[kitd]

    public interface MyWellDefinedBoundary {
        ...
    }

;)

Edit: I should say this is what OSGi was good for. Now it's been replaced, its need is greater than ever.

[bheadmaster]

> well-defined boundaries without having to add the overhead of serialization and network boundaries

Type systems and APIs do that, but only within a single language.