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Human- and machine-readable key comparison reports using the PDF/A-3 format

The BIPM is pleased to announce the publication of the first key comparison report embedding machine-readable (XML and JSON) versions of the document. Use of the PDF/A-3 standard in this way was originally suggested by METAS (Switzerland) in the context of Digital Calibration Certificates (DCC).[1] The recent update of the BIPM.RI(II)-K1.Ce-139 comparison – using the BIPM's International Reference System (SIR) for radionuclide metrology – provided an opportunity to introduce this approach for the first time in reporting a key comparison.


In the context of international key comparisons, the PDF/A-3 format offers the possibility for machines to automatically retrieve key comparison data and the rich metadata associated with it. Key comparison metadata include administrative and technical details of the corresponding measurements, and in the digital world they provide a valuable means of identifying the individual results, and enable advanced data analyses that are not feasible based on a document designed to be read only by humans.

Pending the development of a digitalized KCDB, the adoption of the PDF/A-3 format for comparison reports is a first step towards achieving the FAIR (Findable, Accessible, Interoperable, Reusable) principles.

Example of the use of machine-readable key comparison data - study of the influence of a measurement parameter (metadata) on the results (comparison data) of the measurement service