unitText - What resource do we point users to? about dataspice

[aurielfournier]

units package

https://cran.r-project.org/web/packages/units/index.html

[annakrystalli]

I guess it depends on whether we want to conform with the schema.org unit definition property of variableMeasured.

The unitCode property requires adherance to the UN/CEFACT Common Code (3 characters) or a URL. Other codes than the UN/CEFACT Common Code may be used with a prefix followed by a colon.

But:
a) we are not using unitCode property
b) there is no obvious link to definitive information on UN/CEFACT unit definitions

unitText which we are using, requires text indicating the unit of measurement and is suggested as useful if you cannot provide a standard unit code for unitCode. Given this I'm not sure
which standard we should suggest adhering to in dataspice. UN/CEFACT seems to be geared towards commerce. Perhaps ISO (as per eml2 unit definition) would be more appropriate for our purposes?

Any opinions?

[khondula]

Some other specifications I've come across for my work with ODM2 units

• QUDT: http://www.qudt.org/
• http://unitsofmeasure.org/trac
• https://www.unidata.ucar.edu/software/udunits/

[cboettig]

The units package in R is based on the Unidata units, which include all SI units. I agree that Unidata units are probably a much better choice for us than schema's UN/CEFACT codes. The schema definition for unit code does suggest that you can use other unit codes if you provide a prefix, but this seems not ideal to me (1. not sure what the unidata prefix would be, and 2., most users would find unidata:m a more confusing unit than m.) I think we should stick with unitText, but we should warn if units::as_units() does not recognize the unit?

We could go a step further in using units::as_units to attempt to convert the provided text into a standard form, i.e. units package recognizes these are all the same units:

library(units)
as_units("Meter/sec") 
as_units("m/s") 
as_units("meter / Second") 
as_units("meter * seconds / Second ^ 2") 

EML units are based on the older STMML standard, which I believe isn't really used by projects other than EML now(?).

[amoeba]

Oh as_units is super nice. For match failures I bet we could do a string distance comparison to the controlled list and suggest a few candidates too which might be nice.

[amoeba]

Had a good question in my dataspice demo at NCEAS today that prompted me to think more about this. Could we maybe even warn the user if their unit isn't in a controlled vocabulary? This pushes dataspice further into the territory of metadata quality which I don't think is a bad idea.

[annakrystalli]

Sorry, error, I meant mainly based on SI units in EML

[annakrystalli]

as_units looks great indeed. Maybe we could integrate using units::as_units() to complete the unitText attributes.csv column in the edit_attributes shiny app? 😃