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    When you make a post, you have the option of making it "community wiki" by checking a box at the bottom right of the input field. This has the following effects:

    • You earn no reputation from up/down-votes on that post.
    • Users with 100 reputation can edit the post (for non-CW posts, you need 2000 reputation to edit).
    • If the post is a question, all answers are automatically made community wiki as well.

    Under what circumstances should a question be made community wiki? Certainly any time the goal is to get a sorted list of resources (like Examples of Great Writing), community wiki is a must. But CW is also appropriate for "soft questions" where there isn't really an answer and it seems inappropriate to gain reputation for the question (like Do good math jokes exist? orMost interesting mathematics mistake).

    I'd like to have some kind of a rule for determining if a post should be CW. I feel like this is an important thing to figure out, but I'm not sure exactly why. What do other people think?

    I'm pretty happy with asking all "soft" questions such as the ones you mention be community wiki.

    I think for a hard problem, or one that goes through several iterations of increasingly correct answers, it might be good to have a community wiki answer summarising the relationship between the various answers, and in particular pointing out the conclusion. I know that upvoting attempts to deal with this, but it's clearly not always sufficient. Sometimes an intermediate answer might get upvoted significantly, because it has a great idea, but a later answer actually successfully implements that idea. A community wiki answer might be a useful guide.

    In fact, Andrew Critch's recent question about finite presentations strikes me as a good example -- he kept modifying the question itself to reflect progress, but a community wiki answer clearly would have been better.

    I've added a section to the FAQ explaining community wiki mode. Feedback is most welcome.


    I disagree with this reason for community wiki:

    If it would be inappropriate for you to accept an answer (i.e. you know when you're posting the question that there isn't really an answer), then your question should be community wiki.

    I think that there is a deeper issue about when it is appropriate to accept an answer, and that not all questions where it isn't appropriate should be community wiki.

    There are two obvious extremes of questions: the completely closed form such as my question on fourier series, and the completely open form such as my question on examples of good design of mathematical websites. In the first case, it is clear from the outset that there will be one answer and when I get it then I should (and did) accept it. In the second case, it is clear from the outset that the purpose is to build up a community knowledge base and so it should be community wiki.

    I suspect that in programming, most questions fall into these two categories and there aren't that many in between. However, in mathematics there is a much broader range and most questions fall in between these two. For many questions there will not be one right answer, and it may even be clear at the outset that this is the case. However, I don't think that all such questions should be made community wiki. Making a question "community wiki" sends a signal that it's one of those that should be built up by lots of people contributing a small amount of knowledge - so small that it's not worth assigning any reputation to. Questions like "what's a good reference for X" are obviously in this category. Such questions are hoping to benefit from what might be called indirect experience: the answerer is merely passing on what helped them understand the issue. But I think that any question where the questioner is hoping to benefit from others' direct experience should be worth assigning reputation to, even if there is no intention of ever accepting an answer.

    The question that made me think about this was Tom Leinster's on distributions. It's a marginal case, but he was asking for insight into distributions rather than just references so it draws on people's direct experience rather than indirect experience.

    Let me make one thing clear: this is not an attempt to garner more reputation just because that happens to be my highest-ranked answer! I'm not interested in the reputation system as a scorecard (so long as I stay above Scott Morrison) - it's a way of keeping track of how useful my answers are and of seeing if I'm being of any use to others. But the reputation system is the oil that keeps the system working so community wiki questions should be the rarity rather than the norm. Otherwise, since so many questions won't have definite answers, you should just do away with the reputation system altogether.

    My suggestion for a replacement text is: "A question should be made community wiki if you don't think that people should gain reputation for their answers. A typical case is requests for references where it is the reference that is being judged by the voting system rather than the person who supplied it. Similarly answers should be made community wiki if you don't think that you should gain reputation for the answer. A typical case is if your answer mainly builds upon answers already there, or if you think that it is only a step along the way and you hope others will add to it."

    I should also say that, despite the length of the above, I don't feel too strongly about this. As I use the site then certain aspects jar and so I'm recording them in case others think the same and so that you (the site admin) get some feedback since the worst would be if no-one told you what they like or don't like about the site.

    From the answering perspective, I think the effects on reputation are secondary. The primary effect of community wiki is that it makes your answers easy to edit. I've been making my answers community wiki whenever I think they would benefit from community editing. For example, if I suspect that there are some obvious improvements to my answer that I have missed, or if I am attempting to survey a large field.
      CommentAuthorJon Awbrey
    • CommentTimeNov 11th 2009 edited

    Can other people set the community wiki mode on individual answers?

    I don't remember checking that box, unless maybe accidentally?

    I looked at the FAQ, but it didn't seem to have info on that.


    @Andrew: I think you hit on a big MO limitation.

    Most programming questions are of the form How to do X? Here's an answer! while most math questions are of the form of a conversation Is it possible to do X? Perhaps... But unlikely... Indeed, here's the proof... or How do you think about Y? I think Y is actually coming from Z in cohomology of T... Read this reference... The modern Z viewpoint is here... and even when you think there's an answer you still have What's a coefficient A in B? It's 50 by direct calculation! It's conjectured to be 7^2 + 1 by modular form! It easily follows from Z to be 7^2 + 1, here's an explanaton!

    I'm not sure what is the right course of action to follow from this observation.


    @Jon: The only way a post can be converted to wiki is if the original author or a moderator make it community wiki. These actions leave a record in the edit history, so in the case of the post you're thinking of, you must have just accidentally checked the box. (Edit: I forgot that another way a post can become CW is if it is edited by more than 4 people or more than 8 (?) times, which is what happened in this case.)

    @Andrew: I think I agree with you for the most part, though I think it's fine for users to gain rep even if they don't give a complete answer; they should just have the option of CWing their post to make it easy for others to add to it. I'll probably change the FAQ later today after I've let it stew in my brain for a few hours.

    @David: I would agree that when you're deciding to make an answer CW, that is the primary effect, but when you make a question CW, it's usually not to make the answers easy to edit.

      CommentAuthorJon Awbrey
    • CommentTimeNov 11th 2009

    @Anton: Thanks, it has been an all-thumbs, bleary-eyed sort of day. Is there any way I can undo that?


    @Jon: Nope. Sorry. If this feature-request on meta.SE gets implemented, then it might be reversible.


    I would suggest that, when a thread has many back and forths, as Ilya describes, it would be good for someone to make a CW answer which attempts to summarize the other answers. I've done this a few times (for example, here). I think the best way to encourage this is simply for high profile community members to do it and hope that others follow suit.

    It is possible to write a great summary answer without using CW mode; Greg Kuperberg did so here. But I would think that it would usually be better to use CW, as encouraging everyone to edit should make the answer more likely to correctly reflect the discussion.


    Two questions were flagged to be converted to wiki earlier today:

    They're both "soft" enough that I wikied them to mitigate the bike shed effect. People are likely to spend more time on "easy" questions that anybody can understand and think about. Converting them to CW exerts some pressure to counteract that since you don't gain any rep from CW posts.

    But I did hesitate since converting to CW is irreversible and I still don't feel like I have a good CW policy. So I'd like to bump this discussion and ask for some more opinions. In particular, what do people think of the proposal that all non-math questions should be CW? (questions about being a mathematician or about the mathematical community fall into this category)


    I just worry that I can't see a rationale for this that doesn't also justify banning such questions. I'm increasingly inclined to not community wiki as much. I think a better approach is to close and vilify not-so-great "soft questions", and hope the potential opprobrium of receiving this vilification makes people think twice, unless they really do have a great "soft question".

      CommentAuthorJon Awbrey
    • CommentTimeDec 26th 2009

    Addition, Subtraction, Multiplication, Division, & Vilification.


    I'm completely fine with either community wikifying or community vilifying, but the problem is that you get 10 rep for an upvote and 2 rep for a downvote, so posting mediocre soft-questions is still incentivized, and there's no way we can "mark" people who ask such questions.
    @Anton. Given that the examples you mentioned were both flagged, showing that people support CWing, and devoid of mathematical content, I think you were correct in CWing those 'questions'. I would support a policy that all questions with no maths content get CWed, and believe that if we do agree to such a simple hard and fast rule, then it will make future moderating decisions regarding CW easier.

    @Harry. Yes the voting system is seriously flawed. Unfortunately, I don't think we have any power to change this, though would love to be corrected on this.

    @Scott Morrison: I disagree. I think there's definitely room on MO for questions for which people shouldn't be earning reputation.

    @Peter McNamara: I'll modify the FAQ to say that questions with no actual math should be CW. Both of the questions I mentioned fall into this category. Of course there will still be ambiguous cases, but we'll deal with them as they come up. Hopefully once we have one or two hard rules about what should be CW, random members of the community will start flagging for moderator attention, saying that questions should be wikified (like they do when questions need to be closed). Here are a bunch of examples of questions that should probably be CW but aren't. If nobody objects, I'm going to hit them all with the wiki hammer (which converts the question and all answers to CW).

    @Harry: I know. Increasing the weight of downvotes has been [status-planned] on meta.SO for months. I think they're not doing it because of the pain involved in doing a global rep recalculation and having so many people complain that they've lost rep. I don't know why they don't just leave existing votes with a weight of -2 and increase the weight of future downvotes. A tangentially related thing: if one of your posts is deleted because it accumulated too many spam/offensive flags in a short period of time, you're penalized 100 rep!

    • CommentAuthorJonas Meyer
    • CommentTimeDec 27th 2009 edited
    What about math history questions, like , , and

    (I picked those examples because collectively they are the source of more than 1/4 of my reputation.) I would be totally fine with history questions being community wiki; after all, they are not mathematics.
    • CommentAuthorKevin Lin
    • CommentTimeDec 27th 2009

    I am totally fine with history questions not being community wiki. After all, they are of interest to (some) mathematicians and they (usually?) have definite answers.

    I think any question that can be easily answered by wikipedia should be closed.
    • CommentAuthortheojf
    • CommentTimeJan 3rd 2010
    My RSS feed has floated this rather old question:

    to the top. Should it also be CW? In general, most people mark as CW requests for lists of books, but I don't know how much the moderators should force this.
    I don't understand why a question that has been edited by 4 people, or 8 times by its proposer, automatically goes CW. Why should the amount of editing of a question have any effect on the reputation-worthiness of an answer?


    We've already had this discussion (I don't feel like searching for it, but it was of a length and vehemence quite out of proportion to its importance). None of us have a coherent defense of this rule, but none of us have the ability to change it. At this point it's just a harmless quirk of the system.

    Thank you, Ben. May I suggest that someone find that earlier discussion and put a link to it in the part of the faq list that deals with CW?
    • CommentAuthorWillieWong
    • CommentTimeOct 20th 2010

    @Gerry: I would prefer not. If I remember correctly, that discussion started out with some rather unfortunate feuding, which led into a contentious discussion of the CW issue. While it more or less had a happy ending, the rather meandering way at which the conclusion was arrived, not to mention the amount of our "dirty laundry" in that thread, makes me disagree with its inclusion into the FAQ.

    Of course, Ben may be thinking about a different thread, though I doubt it because of his reference to "length" and "vehemence".

    • CommentAuthorWill Jagy
    • CommentTimeOct 20th 2010
    Gerry, you can search for words or phrases in Meta, the search button near the discussions button. With very common MO terms as community wiki, it will take a while to narrow down to the one you want. I wanted to know early discussions of the word "troll" which was an unfamiliar concept, the search was not that bad as I mostly wanted the earliest one. The outcome was that I indeed learned some things about use of the term.

    On the general point of linking here from the FAQ, I would not be in favour of a discussion here being directly linked. Discussions here are a record of what was actually said, but what should go in the FAQ (whether directly or indirectly) should be the conclusion of that discussion.

    (There's an episode of Yes, Prime Minister where Sir Humphrey explains the purpose of minutes to the PM. He explains that they aren't a record of what was actually said, but what on reflection the parties think they ought to have said.)

    • CommentAuthorCam McLeman
    • CommentTimeOct 20th 2010 edited
    I think in general the FAQ should be updated with some of the stuff which is common knowledge to folks who are active on meta. I think a lot of users would benefit from the knowledge that we can't update most aspects of the software, and hence, for example, we have silly names for our reasons for closing (e.g., "not a real question.").
    @Andrew, it's funny that in this discussion you oppose linking here from the faq list, when the way I found this discussion was from the link in the faq list!

    @WillieWong, I think I found the discussion to which you refer, and I agree no purpose would be served linking that discussion to, well, to anything. I think the concern I raised in the current discussion is not the one that was raised there. There, the emphasis was on the effect on the question; I'm annoyed at the effect on the answers. If 4 people come along and add diacritical marks or tags or re-format the TeX, then no one can gain any points for posting a good answer. Now it's not cool to be overly concerned with piling up points here, but you have to realize that MO is the only place in the mathematical world where I have any hope of having a higher reputation than, say, Bill Thurston; I need every point I can get!

    Seriously, though, I also realize that it's one of those software issues about which we can do nothing but vent. So, I have vented. Veni, vidi, venti?

    I've just had a quick look at the FAQ and so far as I can tell, when an actual discussion is linked then it is clear that it is a discussion. My interpretation of the proposal was that a discussion be linked as an explanation of something. So saying, "Join the discussion here" is fine but saying, "Here's where to find the definitive answer" is not. Hope that's clearer.

    A recent question of mine became automatically "community wiki":
    Actually, I'd prefer to keep it in the preceding state, that seems more suitable for it. In the meanwihile, some people got interested in the question,
    and I would be sorry to have blocked the rep-award for their efforts. Also, I'd rather avoid gathering soft answers, as this question is quite a technical one.
    I've just learned that the reason is the number of edits (I didn't know it)... Actually, I'm not sure I understand this rule; editing a question seems a natural way
    of interacting with the interested people (e.g. adding details at request; correcting; updating etc)
    Bye, P.
    @pietro, you're not the first to be caught, and puzzled, by this feature of the software. It is noted in the faq. There's no convincing explanation for it (well, none that I find convincing) but it seems to be one of those many things we have to live with.

    The explanation I remember hearing the first time it was discussed on meta is that this "feature" is for preventing edit wars (by removing the incentives).