See also: Collaborate With Chemistry.se?

Many of the newer sites have a certain degree of overlap.

With the creation of Chem.SE, I noticed quite a few questions on Physics.SE which could have benefited from the chem community and vice versa. There also are a few that could benefit from bio.SE..

Now these questions don't warrant a migration. They can be double-posted, but this doesn't lead to a smooth experience. Even when cross-linked, changes to either post (new answers,new comments,etc) aren't effectively relayed to the other site, and the two questions are just that-- two, separate questions.

One solution that came to my mind was a "soft migration" option for mods. By this, a question on site A stays on site A. But, it appears in the site B question list as well. Edits/answers should bump it.

Basically, there will be a placeholder item in the questions list of site B. It shows the votes/views/answers of the post on site A, along with the tags (maybe stylized differently). These should be an unobtrusive way to quickly identify what the site is.

The post should also be bumped whenever the post is bumped on Site A, and it should display the rep/time/etc of the bumping user as usual.

Here's a quick mockup of what happens on the site B question list:

enter image description here

Without being obtrusive or in-your-face (stuff like [migrated] is sort of in-your-face), the post is elegantly shown to be on Physics.SE (well, if you know the icon, anyway). The tags are italicized to show that they link to a different site tags, and the "bumping user" (me) has his/her rep on that site shown. We can also add an indicator on the question on site A (like this) that shows that it was soft-migrated. We can use tooltips as well on the icons to tell us why they're here. After all, half of SE documentation is in tooltips.

Now I know that these issues will probably be raised:

  • Rep: An avid user on Site B gets no Site B rep for giving a good answer on Site A. Frankly, I don't care about this to much, but others may.

  • Implementation: It may get complicated. Internally, I'd propose that none of the question data is copied, rather Site A pushes the vote/bump data whenever a vote/bump happens. The easiest way to then implement the soft merge would be to have a table of questions soft-merged "to" site B on site B itself, with columns for all the vote/etc data. The questions table should have an extra column for "soft-migrated to"--that way Site A can determine where to push new data to on every vote/bump. Now, all Site B has to do is take the JOIN of the questions table and the soft-merge table and display them in the new questions list (or any list, for that matter). With some extra formatting, maybe. Of course, I may be oversimplifying this and I don't really know what I'm talking about ;-)

  • Is there a need? : Yes, I would say so. Such questions can get awesome answers is both the communities participate, but our don't-cross-post-much policy deters this. In the end, this will result in better post quality, making the Internet better. Also, as area51 grows, we will see this problem more and more, and this will become more and more necessary.

Thoughts? Any better ideas? Waffles?

Update: Another use case for this would be to soft migrate all MSO questions over to child metas, effectively solving Make network-wide FAQ posts available on per-site metas

  • 10
    +1 Great idea! I have been looking for a solution myself to the same problem! I have seen several posts that could be on both MSO and Area-51 discussion. This solution is perfect!
    – Ephraim
    May 9, 2012 at 12:45
  • @Ephraim: Well, I admit that MSO+a51 wasn't what I was thinking of, but that works too. May 9, 2012 at 12:59
  • Hi @ManishEarth, you may be interested in this conversation. Suppose a soft-migration involved just posting an ad with a link to the question, or showing it on the bulletin board, as opposed to mixing it in with the other questions on the site.
    – jmort253
    Sep 12, 2012 at 2:58
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    @jmort253: Interesting idea. May not be as effective, as the community bulletin is not too noticeable, and one doesn't want to clutter it either. Similar problems with ads--we're trained to ignore them, and I only notice the ads with cool-looking site logos on them. Still, a viable alternative :) Sep 12, 2012 at 6:11
  • What about a special tab? We have "newest", "top voted", "active". What about "shared"? Of course, these mixed questions should only be shown on the parent site, and the question links in "shared" would just take you to that other site.....
    – jmort253
    Sep 12, 2012 at 6:13
  • @jmort253: Ah, so similar to the above, except that the redirects are separated. Interesting, though there may have to be an indicator similar to the bounty one on it for it to work effectively. Sep 12, 2012 at 6:43

3 Answers 3


A certain amount of duplication has always been OK, even across multiple sites; the system doesn't even recognize cross-site duplication as genuine dupes.

The policy on cross-posting has always been an informal one:

  1. In general, you should find the site on which the question is most on-topic, and post it only there.
  2. But if you do post on more than one site where the question is on-topic, you should customize the question for each site's scope, rather than copy/pasting (in much the same way as we deal with copy/paste answers).
  3. A question being on-topic on three or more sites is extremely unlikely, so posting on more than two sites is highly discouraged.

There is a prevailing assumption that, if you post a question on the wrong site, you should wait for the community or a moderator to migrate it to the correct site. But what I'd like to see happen more often is for the OP to move their question onto the correct site, and delete it from the original site. Migrating a question can take a long time, and complications can arise when users start answering the question on the source site, only to have it migrated away.


I support the idea whatever way it's implemented. Recently I had a problem (still not resolved though) that would fit in at least 3 domains: How to aim with a spaceship in 3D considering its angular momentum?

  • The gamedev community: I think they likely had this turn towards target problem before. And probably they would tell whether the player would enjoy playing a game where you control a spaceship this way (mouse aim and the spaceship will turn towards it).
  • The physics community: They don't do maths for the maths sake, someone there probably have experience in the attitude control.
  • The maths community: To help getting grasp with the "optimal control" problem which involves quite a bit of calculus.

Now back to the topic.

The central point of the problem that sites classify questions. Sometimes classification is a good thing: you can classify integer numbers as odd or even. But a number cannot be odd and even in the same time. So classification is fine there. The sets of odd and even numbers are disjoint.

But when there can be overlaps between the domains, classification is simply wrong. It cannot handle the overlapping. What we need is categorization.

And the tool to do categorization is available: tags.

I won't go too deep into the implementation details of this, it probably worth a separate discussion.

For example we can make tag search global, so the entire network can be searched, each question would have 1 implied tag based on which site it's on. So if someone watches the [mathetmatics] tag, he would see all questions on all sites that's tagged with this.

  • 2
    you might want to read blog.stackoverflow.com/2010/09/good-subjective-bad-subjective on why the stackexchange sites model was adopted over this one Dec 19, 2013 at 21:11
  • 1
    @user1937198 I don't see where it says multiple sites are better than having a single site and use tag for categorization.
    – Calmarius
    Dec 19, 2013 at 22:34
  • Its a bit complicated with a lot of the references in the podcasts and i couldn't find anything better but the main point is that having seperate sites encourages a strict focus which leads to better questions. Dec 19, 2013 at 22:36
  • 1
    @user1937198 Did you get it? My answer is one possible solution to the overlapping scopes problem. The tag watchers can still define whether the tag fits for the question or not.
    – Calmarius
    Dec 19, 2013 at 22:58
  • THe problem is that you don't define what happens if a question is simply inapropriate for the stackexchange format. Also you say that off topic content would be tagged and fitered rather than closed so you still be able to answer and vote on them. Part of the closure system is to clearly discourage questions that do not fit at all. Dec 19, 2013 at 23:05
  • 1
    @user1937198 Ok, removed the point about the unwanted content. I'll consider rewording my answer. If something is totally inappropriate, there are other close reasons. By off-topic I meant that the question is asked on the wrong site.
    – Calmarius
    Dec 20, 2013 at 8:52
  • Problem with that is that tags would need a critical mass to work like the current sites. For example atheism.se failed to atract enough people who could answer questions. This is why we have the area 51 process and beta sites. So we would still have to close questions as not having a valid tag to go to. So off topic would still be necessary and more confusing. Dec 20, 2013 at 11:39
  • 1
    @user1937198 why do we need this critical mass thing? In case of sites, it's understandable, we don't want to create and maintain a dead site. But for tags: anyone can create them in the current state too.
    – Calmarius
    Dec 20, 2013 at 20:16
  • The point is that you need people who can answer questions. For tags at the moment the scope of the site ensures there will be people who can answer questions in the tag already on the site. Dec 20, 2013 at 20:56
  • @user1937198 Ok, I removed my inferences.
    – Calmarius
    Dec 22, 2013 at 17:39

I think making the same question appear permanently on multiple sites is clutter. When a question is borderline and unanswered, a migration can give it a second chance, but otherwise I'd leave it where it is.

If the question was asked and answered on community 1 and someone else from community 2 has the same question, the two questions are likely to be different, tailored to each community. Link them to each other to show different perspectives.

A good place to advertise questions on a related topic that were posted on another site is the site's chat room. For example, the main chat room for Ask Ubuntu has a feed that pulls in questions tagged ubuntu from Unix & Linux. The main chat room for French Language has feeds for questions tagged french on Linguistics, Latin and English Language & Usage.

  • 2
    If your chatroom is unused or too busy, feeds don't work. Also, I think we can trust our mods,to handle "clutter" by only softmigrating the good ones. May 10, 2012 at 2:41
  • Also I have never used chatrooms, the content there is not visible on Google and probably only temporarily exist.
    – Calmarius
    Dec 19, 2013 at 19:26
  • @Calmarius SE chat rooms are indexed by Google, but unlike the sites they have very low page rank. Chat rooms conserve their history forever (as long as Stack Exchange doesn't go away). Dec 19, 2013 at 19:35
  • page not found: chat.stackexchange.com/rooms/info/198/mos-eisley?tab=feeds so how does this work?
    – user493924
    Apr 23, 2019 at 17:16
  • @kipbits That chat room no longer exists. I've replaced it by another example. Apr 23, 2019 at 19:13

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