It occured to me that sometimes, the difference between capability and High-level functions is not clear.
For example, in the IFE example, the Capability ‘Provides Satellite and Internal telephony services’ involve the function ‘Provide Satellite communication means’, which are very close (Even if the IFE system does not detail that part).
More generally, what do you think about systematically creating high level functions with the name of the capabilities ? Is that ‘theoretically’ correct ?
Personally I don’t consider ‘Provide Satellite communication means’ very close to ‘Provides Satellite and Internal telephony services’. The scope of the latter is wider than the scope of the former.
Generally speaking, Capabilities and Functions are both concepts used to describe behavioral expectations. But the abstraction level of Capabilities is higher than the Function’s. Furthermore, a Function can contribute to several Capabilities.
Systematically creating high-level Functions for Capabilities is redundant and not always useful.
Hope it helps,
My understanding is that the notion of capability is equivalent to the notion of use-case: a system usage context further described by a set of interactions between the system of interest and external actors; a collaboration between the system and the actors in order to get a specific outcome.
Regarding the labelling of the capabilities, one question would be to decide on the subject of the action defined by the capability: (1) the system or (2) the actors (implicitly by using the system). Both options seem to be valid and practically in use. The first option might lead to a confusion with a system function. The second option might blur the distinction between operation capabilities and system capabilities. I reckon that some recommendations regarding the phrasing of operational/system capabilities may be useful.
When we start a new model, it’s a classic question to ask if this concept is a capability or a system function. In order to answer I ask this question: can I describe this concept by several scenarios or functional chains? Generally it works and sometime I have to go back; but it’s not a big deal, modelling is an iterative process
For me in SA, Capabilities are always Capabilities of the System; they are necessary to “realize” the missions of the system (the goals of the system.
Hello everyone, thank you for your replies.
they have answered perfectly my question : even if both capabilities and high level functions can be ‘technically’ described by a set of functions ( I oversimplified this for the sake of the clarity ), the first ones are gathered ‘behaviorally’ (like Joel said, it is close to the notion of use-case), whereas the second ones are linked ‘technically’.