@ArthurPSmith The only point I would agree with your comment is the case of redirection in case of merging. Even for the addition of end date qualifier I would not accept a change without a modificaiton of the reference: this piece of informetion requires a reference too and was not present in th eoriginal source (the normal case). So this is wrong to add a new information using a reference not mentioning it.

Nudging is not sufficient: no saving should be possible after the change of statement value if no changes are done in the reference section. Most of the references used "retrieved" property as part of the reference so this property has to be updated for each change of the value.

@Jonas. Shoudn't we have something like 'from "" to meter' or '' from meter to km' ?

@Lydia. From my point of view we should constraint the change of the unit with a change of the value (and vice versa) in ordert to reduce vandalism.

@Jonas. Can you give more details please ? So someone adds a value with a unit and saves the edit. So you want to have a special edit summary if someone changes the saved data by modifying the unit only ?

@aude . No info about deployment on https://wikitech.wikimedia.org/wiki/Deployments#Week_of_August_10th. Is it sill planned ?

@Snaterlicious. If you take account of the uncertainty, the copy-paste is not more so important: value + uncertainty + unit, I don't know
if any copy-paste will respect the same interval between the different elements, if the symbol for uncertainty will be recognized, do we need to handle the scientific notation,....

Uncertainty should be described by a set of parameters: lower and upper bounds (not always similar), absolute or relative value and the calculation method. So we need 4 parameters to be able to specify correctly an uncertainty value.

Writing 1.4+-1 means you can't have a precision of 0.4. To be able to write this thing correctly you have to adjust your uncertainty precision to 1.0 so 1.4 +- 1.0 is correct. After for conversion this is another problem.

Some examples already exists and they are some users who can write some infoboxes based on lua and using WD. But the main questions is to define good practice in coding and espacially to avoid bad codes (too long, too many requests,...)

Just find this list for variation of metalanguage: http://www.iana.org/assignments/language-subtag-registry/language-subtag-registry

@thiemowmde. The list will be very long: we have to think a way to avoid scrolling dozen of units to find the correct one. One possibility will be to have for each contributor a personal list which can be uploaded from a personal page like user:User/common.js. The widget compares then the selected value with the official and complete list of units maintained by the dev team (or somebody else) and if there is a match, proceeds to the next step.

We need as starting list of language the languages defined by the ISO 639-3 norm. The best is to sort the list with the three-letter alphabetic codes and then to give the name of the languages in the language of the user. It is very difficult to choose the correct language when it is labelled in original alphabet like 中文（简体） or 中文（繁體）.

If we can discuss about the necessity to have no linguistic content (ISO 639-2 : "zxx) which can be described with the string datatype, we need the undetermined " (ISO 639-2 : "und").