- The Unit Selector is basically an Entity Selector.
- The Unit Selector shall be placed in the widget for entering quantities.
- The selected item is converted to a full URI, and passed as an option to the value parser.
- There must be (at least) one special choice for "no unit" (could also be multiple special choices, e.g. "unknown unit") with the internal value "1".
- Shall allow a unit to be chose from the set of Wikidata (not necessarily local!) items.
Optional / later
- Should allow restriction to a fixed set of URIs
- Shall allow suggestions based on correlation ("which units are typically used with this property?")
- Should indicate whether unit conversion is available for the selected unit