The direct observation of an item for unquantified functionality without use of intrusive instrumentation, fixtures, or excitation. Applicable IFF the characteristic specified is externally observable and need not be quantified.
In theory, we want to do demonstrations at the highest level of system aggregation for which the function is directly observable (in order to provide non-simulated circumstances) AND the full range of circumstances can be experienced (e.g., as resulting from active attenuation of natural environments). The second criterion is the hardest to meet, and may drive the demonstration into laboratory conditions at some lower level. It is also possible that meeting both notional criteria may cause a demonstration objective to be executed in multiple venues of different aggregation. These same arguments apply to testing, as well.
Contrast with analysis, test, and inspection.