Wikidata contains a variety of properties that refer to external resources using standard identifiers for such resources, e.g. ISBN, VIAF, MusicBrainz, GND, etc. itIt should be possible for clients to resolve these to URIs automatically,. either byTeam decision: We includinge the URI expansion in the JSON representation of the respective Statement or DataValue, or by at least including the necessary mappings elsewheras a second DataValue in the JSON documentsame Snak.
Currently, Wikibase knows nothing about the interpretation of external IDs, which are stored and interpreted as plain StringValues. In order to provide URI expansion, a new identifier DataType would be needed on top of StringValue,. The base URI would be recorded as a new "base URI" property in the respective property definitions (in addition to the URL pattern for the formatter; which would contain the URI pattern and perhaps regular expressions for validating and/or normalizingboth can but don't have to be the IDs.same; This additional information would need to be recorded in the respective property definitions (or in a separate vocabulary definition which could be re-used by multiple propertiesteam decision: no fallback for these two URL/URI patterns for now).
NOTE: This ticket only covers the machine readable URI, not the "presentational" URL for the user interface.
(NOTE) TODO: All DataModel specifications (the abstract, the PHP and the JSON one) must be updated to describe the "additional values" stuff.