What exactly are they looking for? What are they trying to replicate?

In T130942#2175494, @Lydia_Pintscher wrote:

What exactly are they looking for? What are they trying to replicate?

Most are wondering why the identifiers are not linked on their own Wikibase installation and don't know that they need to declare the formatterUrlProperty. Pinging @hoo who answered this question before.

I just succeeded in using formatterUrlProperty on a test wiki. Here is my steps:

1. After installation of Wikibase repo, create a property with type String, it can be empty (without any statement), this will be the equivalent property than http://www.wikidata.org/entity/P1630, it is numbered P5 in my case;
2. In LocalSettings.php, set $wgWBRepoSettings['formatterUrlProperty'] = 'P5';;
3. Run the maintenance script php extensions/Wikibase/repo/maintenance/rebuildPropertyInfo.php --rebuild-all --force;
4. Then your properties can declare some P5 with as the value the URL of the destination, with $1 in the URL as a placeholder with the external identifier.

I searched for some time the third step above, I’m not sure if it’s mandatory or if it was because I created the properties (of step 4) before setting formatterUrlProperty.