UMLR — Use cases specifying the same subject cannot be associated: exception

The UML Superstructure Specification V2.4 states in 16.3.6 UseCase (from UseCases): “Two use cases specifying the same subject cannot be associated since each of them individually describes a complete usage of the subject.”

For the longest time, this looked like a common-sense rule. However, it seems to me that in the context of SOA there is at least on exception to this rule.

Let’s say that:
1. The subject represents a component (as understood in SOA) and the use cases represent the component’s services.
2. The initiating actor of all of the component’s services is Another Use Case. This reflects the SOA reality that services are not directly consumed by human actors but by other use cases.
3. The component offers services A and B, both of which trace back to legitimate uses.
4. As it happens, when service B is defined in detail it turns out that one of its steps amounts exactly to the functionality represented as service A.

In such situations, where the subject already has a public service (A) that can actually be reused by one or more of its other public services (B), I think it’s entirely reasonable to allow B to be associated with A. After all, A’s initiating actor is Another Use Case, which is exactly what B is. In object-orientated terms this amounts to an object performing an operation on itself.

I propose for UML to accommodate this scenario.