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Tool for undoing Wikidata merges
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One of the very common Wikidata task is item merging which in most parts works great. Unfortunately some fraction of the merges are wrong, for whatever reasons: cluelessness, vandalism, hasty merges, etc. I see a lot of merges of similar paintings, which have the same title and author, merges of different people with same dates of birth and death, merges of items for portrait of a person with item for a person. etc.

We need a tool for easy un-merge. Right now un-merging involves:

  1. Restoring merged item to the previous version
  2. Restoring redirect to the previous version
  3. The third step should be review of all the links to the new item to figure out which item to assign it to. This step is especially painful.

The unmerge tool should do all those 3 tasks (are there more ?) and we should probably have a link to the undo in the history listing of both items.

Event Timeline

Another thing to take into consideration is that if merge operation triggers changes in Structured data on Commons, than unmerge should also undo those.

Here is an example:

  1. someone did a nonsense merge of Q59165607 and Q55296215.
  2. KrdBot replaces redirected item in all the items linking to it
  3. The merge is undone
  4. At this point all the changes done automatically by KrdBot need to be found and undone manually, as it was done here