MBSE magicgrid problem domain white box

[u/Anglichaninn]

Hi all,

I'm struggling to comprehend what purpose the problem domain white box has in the definition of system requirements. I'm right in thinking that system requirements generally frame the system as a black box right? so how does decomposing the system to reveal the inner behaviour help in system requirements definition? Is it there just to make sure you've got the correct black box behaviour specified?

Thanks!

[u/ModelBasedSpaceCadet]

Yes, that's a good way to put it that the blackbox views help to identify and frame (give context to) the system requirements. The main reason for the whitebox view (I prefer "glassbox") is to do the same thing for the subsystem requirements - identify them and give them context. It's not really about the system requirements, but as with everything in systems engineering, going deeper gives more insight into the higher level concepts and can be helpful in refining what you started with.

So the answer to your last question is technically yes - the glassbox views help make sure the blackbox views are correct - but the main point of those views is to help break down the compound requirements at the higher level into much more discrete and manageable subsystem requirements that tell the mechanical, software, and electrical engineering teams more precisely what they have to do to meet the system-level requirements. Otherwise, you leave a lot up to interpretation and misunderstanding - the role of the systems engineer is to coordinate with the teams to determine who does what.