How to get IWorkItemCommon as a service?

I'm using an AbstractService for some followup functionality and need to get IWorkItemCommon to do some work. The javadoc on IWorkItemCommon says it can be used as a service:
* The work item library provides access to work item specific artifacts. On the client it
* can be obtained as a client library, on the server as a service.
Anyone know the implementation details for getting the service?
Thanks
* The work item library provides access to work item specific artifacts. On the client it
* can be obtained as a client library, on the server as a service.
Anyone know the implementation details for getting the service?
Thanks