For structured data support for Wikimedia Commons we need to enable people to identify for example the creator of an image. This creator can be among others:
* a user on Commons
* a user on Flickr
* a person represented by an item on Wikidata
The person needs to be identified by a plain text name, to satisfy legal requirements. In addition, a URL (resp URI) can be given to uniquely identify the person (or legal entity).
So we need a new Wikibase datatype that covers them all so statements can be made using the same property.
Our current thinking: This would be a new datatype representing a plain text name and an optional URI. The user interface should be "smart" about well known types of URLs - for example, it could have a selector that offers Commons user pages, Flickr user pages and a bunch of others as a drop-down.
Whether the URL would be part of the main data value, or whether it should be provided as a qualifier, is not yet decided. If we use qualifiers, a more complex widget is needed that allows the main value and the relevant qualifier to be edited together. It seems difficult to integrate this nicely with the generic display and editing UI for qualifiers.