*4.1. Metrological Traceability*

Metrological traceability is realized by forming a chain of calibrations that link primary realizations of the SI units to an end user of measurement data. At each stage, influence factors cause the result obtained to differ slightly from the actual quantity of interest. At present, this is usually accounted for by a single uncertainty statement in the stage report. However, influence factors at one stage can give rise to correlations at later stages, and accounting for these effects requires influences to be tracked along the chain [9,10]. That is why the notion of transferability, referred to in the Introduction and the GUM, is important, and comparison analysis highlights this by requiring substantial additional information from all participants, which complements the information in calibration certificates. The study showed that transferability, and hence better support for traceability, is provided by the uncertain number format. In more general terms, the approach to digitalization can keep track of influences and hence identify the *provenance* of contributions to uncertainty in a result.
