As a Wikidata editor, I want to work with normalized quantities in the query service, even if the source data is specified using rather unusual units.
The unit conversion (configured in [unitConversionConfig.json](https://gerrit.wikimedia.org/r/g/operations/mediawiki-config/+/478738df203fee660b2ed1d6481a26423daaf696/wmf-config/unitConversionConfig.json)) has not been updated in three years (last changed in August 2017). In the meantime, a lot more units on Wikidata have gained conversions to standard SI units: re-running the maintenance script which generates the config file grows it by a factor of three, and @Toni_001 states that over a thousand units were added (and also that the current state of units on Wikidata is overall much better anyways). See [project chat discussion](https://www.wikidata.org/wiki/Wikidata:Project_chat#Coherent_SI_units) ([permalink](https://www.wikidata.org/w/index.php?title=Wikidata:Project_chat&oldid=1304783674#Coherent_SI_units)).
However, it looks like we’ll need to update that maintenance script a bit before it can be used – when I ran it, the conversions it produced converted units like millimetre and centimetre to themselves (with a factor of 1) rather than to multiples of metre with the appropriate factor. (Personal comment: the script also has a few parameters for configurable Item IDs and then hard-codes a whole bunch of other Item and Property IDs, so I expect it’s not useful for third parties at the moment. Maybe we can improve that too?)
(None yet – there doesn’t seem to be any popular unit that’s currently grotesquely wrong and would require an update ASAP, just a bunch of smaller units that could use the improvement.)
* Can we get this done ahead of the apparently-upcoming WDQS reload (T267175#6613631)? Otherwise the changes won’t be fully effective until the next reload.
* @Gehel would it cause any issues with the streaming updater if the same revisions produced different RDF due to changes to the unit conversion config? Do we need to coordinate deploying this with you?