The abstract notion of a service has nothing to do with an execution model. It simply means a well defined interface to some meaningful unit of functionality.

The abstract notion of a service has nothing to do with an execution model. It simply means a well defined interface to some meaningful unit of functionality. Properly designed, the execution model is orthogonal and the service itself doesn't care if it's invoked in-process or not. It delegates that to some other manager, which probably has a service interface of its own. It's about sane abstract system boundaries, not mapping to real world facilities.