Based on the feedback so far I have frozen the datatype for time [1] and updated the datatype for coordinates. There are now two distinct members:
* precision: which actually means the precision in the representation, i.e. by the degree or arcsecond, etc., and which is used to calculate different representations
* dimension: which represents the "size" of the object / target area in meter, and which can be used to choose the scale for a map or to represent uncertainty about the coordinate [2]
The dimension parameter is based on the work of Max Semenik in the GeoData extension and recognized as a solution to the discussion that happened here on the list.
If you have any further comments on the datatype for coordinates, say so here. Otherwise I will move to quantities next :)
Cheers, Denny
[1] http://meta.wikimedia.org/wiki/Wikidata/Data_model#Dates_and_times [2] < http://meta.wikimedia.org/wiki/Wikidata/Development/Representing_values#Coor...
[3] https://www.mediawiki.org/wiki/Extension:GeoData#Glossary