The IEC has defined a lot of semantic IDs, e.g. for units.

As you can see in the example of ' pressure coefficient', there are

  • 0112/2///62720#UAA576 - kilopascal per kelvin
  • 0112/2///62720#UAA216 - megapascal per kelvin
  • 0112/2///62720#UAA259 - pascal per kelvin
  • 0112/2///62720#UAA528 - hectopascal per kelvin
  • 0112/2///62720#UAA811 - millibar per kelvin
  • 0112/2///62720#UAA324 - bar per kelvin
  • 0112/2///62720#UAA702 - pound-force per square inch per degree Fahrenheit

More details are then available per unit: https://cdd.iec.ch/cdd/iec62720/iec62720.nsf/Units/0112-2---62720%23UAA576?opendocument

The data seems to be stored in a Lotus Notes database, and it's not accessible in an automated way.

Is this data also available for download in a machine-readable way?

Minimal dataset:

  • data: IRDI (semantic ID) in latest version, preferred name, short name in separate columns
  • context: I want to assign semantic IDs to the units I use
  • region: Germany and Switzerland
  • license: free to use (no money involved)
  • authority: IEC
  • requirements: N/A
  • non-answers: pointing to the CDD as linked above

Ideal dataset:

  • other columns as listed in the example: version, revision, definition, release date etc.

1 Answer 1


In short, use this link, click "select all", and click "export selected": you'll be able to retrieve an Excel file with the data you're looking for.

How to get to this page in the first place? You visit their local search engine, select the option "Units", and enter an asterisk (*) as a search term.

The Excel file may require some cleaning from your part (e.g. there are a lot of empty rows at the beginning of the file), but it should contain most of the information you're looking for, including ID code, preferred name, short name, version number and release date, revision number and date.

The license and terms of use for the data are available here: https://cdd.iec.ch/cdd/iec62720/iec62720.nsf/License (note that they allow free use only for some data, not for all, so you may want to check what you can or cannot use). A more general presentation of the database is available on the website homepage, including contact information for any queries.

Note that in case you're trying to retrieve data for other items than just units, their search engine seems to limit the number of results to 5,000 by default (not a problem if you're only interested in units, as there are only about 1,800, but possibly a problem for other kind of data). There is probably a reason for this default limit; if this is a problem to you, it might be a good idea to contact the people who manage the website, and ask them how and under which conditions (if any) you can circumvent this default limitation.

NB: I'm not related in any way to the IEC organization, so I can't provide much more information than that.

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