RDF representation has two ways of representing a value: simple and full. While the full value includes the unit and thus represents the full information about the value, the simple value currently does not have any unit information.
The purpose of this task is to develop a way to represent unit in the simple value, if possible.
Current proposal (derived from https://etherpad.wikimedia.org/p/Wikidata_Meeting_Berlin_10262015) and attached pictures, is:
- Each property can have primary standard unit
- If the current unit can be converted to this unit, it is represented as xsd:decimal
- Otherwise, if the unit is not "1", it is listed as "1234"^^wdu:Q1234, where wdu:Q1234 is defined as:
wdu:Q1234 rdfs:subclassOf xsd:decimal, wikibase:measuredBy wd:Q1234
The wdu: units are generated on the first use and there will be a mechanism preventing (or reducing if full prevention is too expensive memory-wise) their duplication.
If the property has no standard unit defined, the values are converted to normalized units (see T117031) and presented as above with their units.