What would be a proper term for a type of evaluation which is performed "from the outside" of a system (i.e., without inspecting the internals of the system)? I would also like to know the opposite term, that is, when it is necessary to examine the "interior" of a system for performing an evaluation.
I want the term to be as general as possible, since I'm trying to use it for classifying measurement processes of a system. From an abstract point of view, when measuring some aspect of such system, one option is to measure it without checking the "inside" (i.e, "from the outside"), while the other option would be to actually look inside the system.
We can assume that the system is opaque, in the sense that external observations does not provide a view of the inside (as in the X-rays example from the comments).
The particular context is the evaluation or measurement of IT service providers. These entities are opaque since it is usually not possible for an external evaluator to inspect the internal workings of these providers, but only to perform observations on their services. On the contrary, when this evaluator is granted access to inside the provider, as in the case of an audit, then the evaluation can be done from the inside. Said that, I would like a term as general as possible, since I want to make a general classification of measurement and evaluation procedures.
It reminds me of the terms "black/white-box", but I would prefer a more "formal" term. "Internal/external" is also an option, but for me that would mean examining the interior vs the surroundings.