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I've never seen a tag synonym created via the voting mechanism and I see evidence that the system isn't working to create synonyms without moderator intervention.

Does anyone have any figures about the number of synonyms that are create by votes as opposed to the number created by moderator fiat across the network?

Related: how many synonyms have been voted down and how many never get any votes at all?

Finally, do the numbers suggest any way the current system can be improved? Should the suggestion system be scrapped altogether?

As a side note, the tag synonym suggestion system on most meta-sites seems unlikely to ever work since voting is different on meta and fewer people participate there. Recently, I noticed a site had both and . With a tag score of 2, I couldn't suggest a synonym. Even if I could, there's no chance it would be acted on by other users. So I asked a moderator in chat to fix it. That was a better plan all along, so why do we offer the suggestion system on meta to be a source of false hope?

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The evidence questions you cite are tag merge requests, an operation that is only available to diamond mods. But you're right; it's difficult to get a tag synonym request through with just community votes. –  Robert Harvey Mar 29 '12 at 21:41
It's completely unused on any SE 2.0 site as far as I can tell. SO might have the numbers to actually create a synonym that way, but on SE 2.0 sites synonyms are created purely by mods in my experience. –  Mad Scientist Mar 29 '12 at 21:47
@Robert: I guess I'm confused. Take this request: isn't the end result (however it's phrased) that wildcards is mapped to wildcard? Should we encourage users to continue to suggest synonyms or should they post a request on the relevant meta to get tags "merged" instead? –  Jon Ericson Mar 29 '12 at 21:54
@Fabian: that's my experience as well. I was curious if even on SO the system works since it seems a post to MSO is still required to get the process moving. –  Jon Ericson Mar 29 '12 at 21:56
There are definitely suggested synonyms that get approved through the existing system. I've personally cast the 4th and final vote in favor of 3 or so, and I believe I've had one or two of my own approved. But it does seem there's not enough participation there and that while what Robert says is true, most of the "tag merge" requests would be better or at least adequately served via the creation of a synonym. It's unclear to me why mods don't periodically go through the list of pending suggestions and approve the obvious ones. There are a lot that I think are obvious still pending. –  Cody Gray Mar 29 '12 at 21:59
Most of the time, we do perform a merge as part of the synonymization, but not always. –  Robert Harvey Mar 29 '12 at 21:59

3 Answers 3

up vote 24 down vote

Clearly, the vote requirement exists to make sure that the synonyms are correct (ie created by one who has knowledge of the topic). To my experience, this system fails, because most synonyms are discovered by coincidence.

  • Work-around
    (Temporarily) retag a question, on which you've posted an answer with at least 5 upvotes. Wait a little bit, then suggest / vote on a tag synonym.

    I haven't practised this idea yet, because it doesn't feel OK to deliberately add wrong tags to a question, polluting the revision history of the question.
    How do you (the Community) rate at this approach?

  • Solution 1
    Allow users with sufficient reputation (10k+, 15k+, 20k+?) to cast (a half?) vote on the tag synonym. This is based on the fact that reputation is a "measure of how much the community trusts you".

  • Solution 2
    Allow users with sufficient votes in the tag cloud (related tags) to vote.
    This concept is based on the assumption that tag synonyms usually have an overlapping tag cloud, and the likelihood that a tag synonym is found on a question in your field.
    (Josh has framed this suggestion has as a feature request, see: Count related tags fractionally when determining eligibility for voting on synonyms)
share|improve this answer
I've actually attempted the work-around and it didn't work. (This was on an SE 2.0 beta site, to be sure.) My feeling is that unless there's some good way to "advertise" a possible synonym, there won't be enough traction on it no matter how low the bar is. Right now, the best way to make tag synonym suggestions visible is to post in the site's meta. Then a diamond moderator will usually make the call. –  Jon Ericson Apr 10 '12 at 22:52
@JonEricson "Wait a little bit" can take up to 24 hours, I believe. Did you get +5 votes in both tags? –  Rob W Apr 11 '12 at 8:11
Sorry. I was unclear. I was able to suggest synonyms, but the suggestion fails to be acted upon. It's largely a case of out-of-sight/out-of-mind. Before I put excess effort into conforming to the suggestion system's rules, I was curious if the system works at all. It sounds like on StackOverflow it sometimes works. But on a smaller site, asking a moderator is a far more certain plan. –  Jon Ericson Apr 11 '12 at 8:33
@JonEricson We can relieve moderators by forming a per-site group, which reviews suggested tag synonyms, using the work-around if it is generally considered acceptable. –  Rob W Apr 11 '12 at 8:47
@JonEricson why was it never tried to simply create a review queue for them? I was thinking this morning about how tag synonyms always require mod intervention on P.SE (and on lower volume sites than SO altogether this is probably always the case), and my thought was make it a simple privilege just like the others: 7.5k or 10k or whatever required, 4-5 votes required to pass it, and a review queue to ensure it gathers those votes, the last part was obviously key when I thought about this as tag suggestions would quickly be overlooked. –  Jimmy Hoffa Sep 16 '13 at 14:45
Alternatively you require X rep in the tag for it to show up in your review queue (regardless of site rep or along with X minimum site rep) but as you mention, visibility is a requirement and review queues were invented for precisely this reason. –  Jimmy Hoffa Sep 16 '13 at 14:47
@JoshCaswell Nice. I've added a link to your suggestion inside my answer. –  Rob W Dec 7 '13 at 21:42

The below answer has been brushed up and turned in to its own separate : Improving Tag Synonyms

This is definitely an issue, as I look at my poor unfrequented tag, and its proposed synonym sitting with a lowly zero votes and a single person with sufficient reputation to actually support it active in the tag:

Answer more [tag:google-visualization] questions so that you can approve this synonym

The existing 3 synonyms I asked for in the Tavern on the Meta (prior to receiving 2500 reputation) and a mod kindly made the change.

I do not believe a standard review queue would work. If it is anything like the Suggested Edits or First Posts queue, then there will be a lot of mindless clicking of accept resulting in a lot more of an issue than an inappropriate edit, or a poor quality post. And that isn't the goal. If anyone can click accept and improve the system, then suggested synonyms shouldn't be suggested at all, and just be accepted straight-up.


Remove Silly Limitations

Johnny Stack has 4,000 reputation and a score of 200 in the tag. changes the official name to so all sorts of new questions start popping up with that tag. Johnny Stack wants to suggest making a synonym of but is rejected with a silly message:

Silly Error Message

So Johnny can retag his old questions with the new tag, get the 5 score, and then suggest the synonym just to meet this arbitrary requirement. Those edits will be entirely useless when the synonym gets approved. Making those edits to his old posts will not improve his understanding of the tags in the slightest and will simply add another hoop for him to leap through.

Alternatively, he could suggest that is actually a synonym of , but this is definitely not actually true. But at least it could be proposed! And there would be more people able to actually accept it because it is the existing tag with more people paying attention to it. But this is not a solution, it is a problem masquerading as a solution due to it being a practical alternative.

Make the Synonym Approval Process Visible

Right now you have to visit the tag synonyms page to see that there is a synonym request, and to vote to approve it. Nobody does that which is why these things never get approved. Instead we should take a two-tier approach to getting users in that tag to notice the suggestion:

  1. Give anyone with that tag favorited a notification
  2. Have a nice banner appear to anyone with 5 score in that tag who is browsing the tag

Giving users who have the tag favorited will give them an opportunity to click the notification and vote. This is an incredibly non-intrusive way to let people know about tags they have already stated they care about, and potential ways to improve them.

People browsing the tag who meet the criteria to vote could just have a nice banner saying something like:

[User] proposed that is a synonym of this tag. What do you think? [Yes/No]. For more details see [Link to Synonym Page] (X)

You can raise the bar for how many votes it takes to account that some people won't think in depth, users can ignore it and it won't come back, and it will only target people who are currently interested in the tag and can do something about it. Improvement becomes easier while minimizing the hassle to the user.

Improve Synonym Suggestion

Instead of this dull suggestion box:

Minimalism in Dialogs

We could add space for people to add a comment, add information on the tag wiki (excerpt with a link to full description) for the suggested synonym, and put it all in the same place allowing users to more easily determine if they are related. Then when a user wants to find details they don't have to do the legwork themselves minimizing the burden on them. It also allows the person suggesting to make links to things that explain why they are synonyms. Win-win for everyone involved. And less burden on the moderators.

share|improve this answer
I agree. Participation in tags with smaller audiences gets lower scores than popular topics, where the audience is much greater, with magnitudes more potential votes. But I would think expertise in "niche" subjects is exactly where contributions like syntax synonyms could help funnel questions with low quality tags into better visibility. What's the point of awarding a "create tag synonyms" privilege that can't be used? –  WarrenT Aug 24 at 14:03

Tag Synonym Statistics at Top Network Sites

To analyze this, I used the Stack Exchange Data Explorer to classify tag synonym suggestions into three categories: approved by vote (approved with score >= 4), approved by mods (approved with score < 4), and pending. As far as I can tell the data explorer doesn't include information about tag synonyms that were rejected.

Here are the results for the top 11 Stack Exchange sites (by question count):

                     Site  Mods  Vote Pending
           Stack Overflow  1602   804     750
              Mathematics   164    17      12
               Super User   770     1       1
             Server Fault   296    25       2
               Ask Ubuntu   273     3       5
              TeX - LaTeX   149     9       5
      Meta Stack Exchange   303    18       1
           Unix and Linux   117     1       7
Stack Overflow на русском    91     3       4
            Math Overflow    54     1       3
     Statistical Analysis   151     0       2
                    Total  3970   882     792

In summary, tag synonyms do get approved by vote, though not as often as they get approved by mods. 33% of the synonyms on Stack Overflow were approved by vote, and only 3% of the synonyms on the remaining sites were approved by vote.

Among the pending flags on Stack Overflow (the only site with more than a handful), there are 50 with score -1, 449 with score 0, 134 with score 1, 81 with score 2, and 36 with score 3.

Why Don't More People Vote on Tag Synonyms?

I think the high rate of approval by mods is because folks go straight to meta with their synonyms, perceiving that their proposal will otherwise languish in the proposed tag synonyms list. It has certainly been my experience that tag synonyms languish in review, and jmac estimated that on average pending synonyms have been around for nearly half a year. Why not go straight to the mods if you have to wait half a year or more for approval?

I see two hypotheses for why people don't vote on tag synonyms -- they either don't have a high enough answer score in the tag or they do but still choose not to vote for any number of reasons (UI makes it hard to find the voting page, voting is not properly incentivized by badges, etc.). To explore the degree to which these two factors play a role, I've broken down the number of users able to vote on each of the 612 target tags for the 750 current pending tag synonyms on Stack Overflow (note the log scale on the x-axis):

enter image description here

For 8% of pending synonyms, there is no hope of approval because there aren't four eligible voters on the site. 14% of pending synonyms have 10 or fewer potential voters, so they aren't likely to get approved by vote. On the other hand, many pending synonyms have a large number of potential voters -- 47% have at least 100 potential voters and 8% have at least 1,000 potential voters.

Potential Fixes to the Tag Synonym System

The fact that there are 750 pending tag synonyms on Stack Overflow and that 97% of the synonym approvals on the next 10 highest ranked Stack Exchange sites (by number of questions) are done by mods suggests that the tag synonym voting system leaves much to be desired. I think the least controversial way to deal with the issue would be to get more eligible voters to actually vote on synonyms. Many good proposals already exist on meta for doing this:

  • Create a badge for voting on tag synonyms, as proposed here. The "go get it" link from a user's profile page could link to the list of tag synonym proposals that the user can vote on.
  • Create a tag synonym review queue, as proposed here. The badges that exist for all review queues could be applied to incentivize voting.
  • User interface improvements such as notifications for tag synonyms you can vote on and a link to pending synonyms when browsing a tag, as proposed here.


Within the Stack Exchange Data Explorer, I used the following query to break down tag synonyms by type:

    CASE WHEN ApprovalDate is NULL THEN 'Pending' ELSE NULL END,
    CASE WHEN Score >= 4 THEN 'Vote' ELSE 'Mods' END
  ) AS type FROM TagSynonyms) AS a
GROUP BY a.type;

I got the breakdown of pending flags on Stack Overflow with:

FROM TagSynonyms
WHERE ApprovalDate is NULL

To get information on the number of folks who can vote on each target tag, I used:

SELECT tagScores.tn, COUNT(*) FROM
  (SELECT target.tn, a.OwnerUserId, SUM(a.Score) AS scoreSum FROM
    (SELECT DISTINCT(TargetTagName) AS tn
     FROM TagSynonyms
     WHERE ApprovalDate is NULL
    ) AS target
  INNER JOIN Tags AS t ON target.tn=t.TagName
  INNER JOIN PostTags AS pt ON t.Id=pt.TagId
  INNER JOIN Posts AS q ON pt.PostId=q.Id
  INNER JOIN Posts AS a ON q.Id=a.ParentId
  GROUP BY target.tn, a.OwnerUserId
) AS tagScores
WHERE tagScores.scoreSum >= 5
GROUP BY tagScores.tn;
share|improve this answer
Very well done. The numbers certainly help clarify the problem: the synonym voting system kinda works on Stack Overflow, but nowhere else. Thanks for clarifying things. –  Jon Ericson Sep 4 at 23:30

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