Codelists for unitOfMeasure

[practicalparticipation]

At the moment we allow a string for unitOfMeasure. We should move towards a recommended codelist for this.

This thread provides a good summary of the options, which include:

• UCUM - very comprehensive, but license terms are slightly restrictive (e.g. from quick interpretation I think it makes it impossible to locally extend should a unit required not be covered - although this is unlikely given comprehensive nature)
• UN/CEFACT Recommendation 20 - providing detailed spreadsheet, and potentially already in use in trading contexts.
• NASA QUDT Unit Ontology - a smaller set of properties, but seems to include major ones, and under a Creative Commons license.

Ideal approach to work out what codelists might be valid here would be to go to our existing data and see if any existing codelists are in use, or to check if there are units of measure in use in existing data which will not map well to one or more of these lists.

[myroslav]

NASA QUDT is quite good one, but how can I have just "Items"? Should I omit the "unitOfMeasure" altogether then?

[myroslav]

BTW, the UN/CEFACT Recommendation has SI units and equivalents in Annex I (so called "normative units"), and Annex II and III are covering so called "informative units", and include something like "piece", "spool", "strip", "stick", "thousand piece", "ten thousand sticks", "dozen piece", "bulk pack", "pair", etc.

It look like NASA QUDT Unit Ontology is missing these "informative units". Am I misreading it?

[practicalparticipation]

The one issue with NASA QUDT is that includes currencies also - in a way that could lead to some confusion with our currency codelist potentially.

It does look like QUDT misses the informative units, and some of those informative units (e.g. piece) might be quite useful to us.

@birdsarah Where should I look to see if any of the data we encountered in the supply side research had codelists for units of measure?

[birdsarah]

The only one we found was Uruguay - see https://www.comprasestatales.gub.uy/consultas/ConsultaComprasDetalle.php?IDCOMPRAS=447851&familia=0&subFamilia=&clase=&subClase=&codArticulo=&v=portal&s= - I didn't find the documentation to be able to answer about code lists.

See our list of goods & services supply side fields here: http://ocds.open-contracting.org/opendatacomparison/datamap/field/42/

[birdsarah]

@practicalparticipation Is there anything to do here for RC?

[practicalparticipation]

Note to self: value = value per unit (as in hours at $20/hour), then 22 of them in quantity.

[myroslav]

FYI, I'd managed to find "Recommendation N°. 20 - Codes for Units of Measure Used in International Trade " at http://www.unece.org/tradewelcome/areas-of-work/un-centre-for-trade-facilitation-and-e-business-uncefact/outputs/cefactrecommendationsrec-index/list-of-trade-facilitation-recommendations-n-16-to-20.html URL, the one form ticket description is invalid at the moment.

[practicalparticipation]

Flatting this as post 1.0 as I think it's going to need some more in-depth use-case work. However, @myroslav - if you have a live use case and want to use the now documented extension approach to handle that this would be great.

[myroslav]

I'll have a look at extensions and will post pull request with one that will document the units approach we'll utilize.

[ekoner]

Prozorro are using Recommendation N°. 20 - ready for evaluation.

[akuckartz]

I would prefer links to skos:Concepts instead of strings.

[akuckartz]

... but the QUDT ontology might be even better.

[ekoner]

Links to:

1. QUDT ontology http://www.qudt.org/
2. SKOS primer https://www.w3.org/TR/skos-primer/

[timgdavies]

A full proposal is now given in #366