Wikibase follows the maxim that values should be stored as given in the original source. The notation should be normalized, but the value should remain unchanged, using the original unit of measurement, calendar, time zone, reference globe, etc.
However, for consumers of the data, it is convenient to have values normalized, converted to some form that makes it easier to compare values. The solution is to optionally include additional forms of the value next to the "datavalue" field in the snak structure in JSON output. The following forms should be supported:
* datavalue-uri: Full URI form of external identifier internally represented as simple ID strings. URI form of referenced entities.
* datavalue-normalized: Time values converted to UTC (gergorian); Quantities converted to base (SI) units.
At least datavalue-uri should be included per default in the output of Special:EntityData, since only this feature turns the output into true Linked Data. All supported expansions should probably be included in JSON dumps, for easy import/re-use. For API output, these should be optional.