A small mechanical note for those not familiar with Wikidata's internals (since it took me a while to figure this out):

"Preferred" and "Deprecated" are "Ranks" (the third is "Normal") and the rank can be set by clicking the "Edit" button and then clicking on the leftmost of the two tiny sets of three stacked buttons near the left of the input field.

It seems like the constraint checker could check for either only one "Preferred" or all but one "Deprecated" which would allow editors to evolve in whichever way they wanted.

Tom

On Thu, Oct 1, 2015 at 12:40 PM, Tom Morris <tfmorris@gmail.com> wrote:

On Thu, Oct 1, 2015 at 4:19 AM, Markus Krötzsch <markus@semantic-mediawiki.org> wrote:
On 01.10.2015 00:58, Ricordisamoa wrote:

I think Tom is referring to external identifiers such as MusicBrainz
artist ID <https://www.wikidata.org/wiki/Property:P434> etc. and whether
Wikidata items should show all of them or 'preferred' ones only as we
did for VIAF redirects
<https://www.wikidata.org/wiki/Wikidata:Requests_for_permissions/Bot/SamoaBot_38>.

Now if the external site reconciles the ids, we have these options:
(1) Keep everything as is (one main id marked as "preferred")
(2) Make the redirect ids deprecated on Wikidata (show people that we are aware of the ids but they should not be used)
(3) Delete the redirect ids

I think (2) would be cleanest, since it avoids that unaware users re-add the old ids. (3) would also be ok once the old id is no longer in circulation.

I agree #2 is best, although #1 could work too. The problem with #3 is that an identifier, once minted, is never "no longer in circulation." This is precisely why Wikidata items are never deleted. There's always the possibility that someone will hold a reference to it somewhere. Thad's use case isn't uncommon.

Is there any benefit in removing old ids completely? I guess constraint reports will work better (but maybe constraint reports should not count deprecated statements in single value contraints ...).

The constraint reports definitely need to be fixed. I recently saw a reference to a VIAF bot run that deleted a whole bunch of VIAF identifiers to "fix" things being flagged by some constraint.

Other than this, I don't see a big reason to spend time on removing some ids. It's not wrong to claim that these are ids, just slightly redundant, and the old ids might still be useful for integrating with web sources that were not updated when the redirect happened.

Rather than not wasting time removing, I'd like to see affirmative statements that keeping them is a good thing. If people find them annoying or cluttering, it's because of poor UI design, not because they lack usefulness.

Tom