Updated version (March 20, 2011):

Use this tag if:

  • well-known open problems: the problem is equivalent to a well-known open problem in the literature
  • community open problems: the question is not answered after considerable time and the community decides that the question is an open problem (meta can be used for discussions)

cstheory is not the right place to ask well-known open problems. You should post questions you're actually seriously thinking about. If you're thinking about a well-known open problem, provide some background and ask about something specific related to the problem, like "Such and such is a well-known open problem. So-and-so proposed this and that approach. Does anybody know if this aspect of their proposal can be made to work under these circumstances?" If you want to contribute to (or view) a list of open problems, visit the Open Problem Garden.

If it turns out that a problem is equivalent to a well-known open problem, then the tag is added. After that, the question essentially becomes, "What is known about this problem? What are some possible ways to approach this problem? What are some ways that people have tried to attack it before, and with what results?" That way, the cstheory thread for the problem becomes a repository of resources related to the problem. Perhaps the answers could be organized by approach, with an outline of the basic approach, followed by a horizontal rule and a summary of what is promising about the approach and why it doesn't give a complete solution.

To join the discussion about how cstheory should deal with open problems, go to this meta cstheory thread.

The 's tag wiki is based on MO's FAQ on open-problems.

  • $\begingroup$ There was a previous post about how we should use the [open-problem] tag, but I cannot find it right now. $\endgroup$
    – Kaveh
    Commented Mar 15, 2011 at 4:17
  • $\begingroup$ Other than Peter's suggestion, I'm fine with this wording. $\endgroup$ Commented Mar 19, 2011 at 15:46
  • 1
    $\begingroup$ The 80's are a lot longer ago in TCS than in math. Maybe we should reword this sentence to "So-and-so has proposed this-and-that approach." Aside from that, it looks fine to me. $\endgroup$ Commented Mar 19, 2011 at 17:56
  • $\begingroup$ We may want to add an exception for polymath questions. $\endgroup$
    – Kaveh
    Commented Mar 20, 2011 at 9:26

1 Answer 1


Maybe you should say "cstheory is not the right place to discuss famous open problems." Lots of people have asked about less well-known open problems, some of which have then been solved.

  • $\begingroup$ I see, good point. I don't think we have solved any open problem on the site(in the first common sense of being equivalent to an open problem in the literature, if we did that would be great) but since we have decided to use the same tag for community decided open problems it causes confusion. I think I can fix it by distinguishing between them and being more specific in the later part and restricting it only to well-known open problems. $\endgroup$
    – Kaveh
    Commented Mar 20, 2011 at 8:39

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