On 07.06.2015 20:07, Luca Martinelli wrote:
Il 07/giu/2015 17:19, "Markus Krötzsch" <markus@semantic-mediawiki.org mailto:markus@semantic-mediawiki.org> ha scritto:
Coming back to Magnus's suggestion ... I think the existing property
"retrieved" (P813) could be used for this "last verified on" property, that is, for setting the time a which some external reference was last compared to a claim in Wikidata.
Magnus also pointed out that many external IDs are "self-verifying"
in that they are their own reference. The situation is somewhat similar for homepages. Should we adopt the practice of giving a single retrieved value (without any further information) as the reference for such cases?
Adding P813 dates more widely would also open up new ways of
maintaining data, since one would have a way to filter statements by how long ago they had last been checked.
Sounds ok, but how will we do it?
As editors, we can just do it from now on. I was always unsure what to use as a reference for ids and homepages. Now I'll use this.
Bot operators can do the same. Magnus is already using P813 in the sourcerer game as well.
I don't know if there is a good place on Wikidata to document such things. I always struggle to find documentation about how to do references (best practices, e.g., how to cite an online news portal correctly).
And should we wait for the identifier datatype to be ready?
Time information makes sense for any online reference, so we do not really need to know if the statement we are editing is for an ID property. Whether a statement is "self-verifying" so that a single P813 would already work as reference depends on the context. The properties that this is mainly true for are those of type URL and those where you can get a URL or URI to verify things (i.e., those with properties P1630 or P1921).
Markus