Reading Frank's proposal and DODAF exercise on the service definition, I've caught myself on the mismatch between what we understand as SOA Service today and what was written in RM.
For the last couple of years, I identify service via its business functionality and RWE. I believe. Ken would support me in this (we discussed this a few years ago). Thus, a service (this is not an attempt to set new definition butrather the meaning of the entity) is something that Offers and Provides certain business functionality ('business' in this context may be anything -from a calculation of credit risk to washing clothes), and Delivers RWE (to theWorld).
In contrast, RM defines a service as:
"A service is a mechanism to enable access to a set of one or more capabilities, where the access is provided using a prescribed interface..."
That is, "a mechanism to enable access to" perfectly fits with the definition of an interface; this is why many claim that Web Service technology and WS WSDL are services.
So, the problem is: "a mechanism to enable access to" does not properly reflect characteristics of the service such as business functionality and RWE.
Now, let me ask two questions:
1) if Service=Interface, how anybody can guarantee that particular business functionality is present and available? An interface may lead to anything and this anything may be simply invisible through the interface...
2) does any interface deliver any RWE?
Here is a set of example questions:
a) does a car door provide any car's functionality and move the passenger from A to B?
B) does a door and even receptionist on the laundry shop defines the what the laundry does?
C) if an interface accepts arbitrary commands (while the semantics of the commands is managed separately), can such an interface tell us anything about the business functionality to be triggered by particular command?(Actually, this Command-model is what I usually use with the Web Services)
IMO (shared by many SOA experts), SOA Service is the combination of operations performed manually and/or automatically that together offer and provide certain business functionality and deliver RWE. To provide certain business functionality and deliver RWE, the service utilises certain capabilities. The RWE is delivered to the World, not necessary to the requester. The service may have as many prescribed interfaces as needed for its different consumer audiences and interaction channels. This understanding of the service positions the SOA Service right in between Business and Technology and opens the door into the Business Service-Oriented world.
Sorry for so many words. I am afraid this problem with service definition is quite serious.