I asked a question ("Meaning of acronym SSO"), which was "closed as exact duplicate" as another ("How is std::string implemented?"). But the close requests triggered a discussion, in the comments, about whether the question really was a duplicate. Several of the commentators have high SO reputation, suggesting the duplication is of a kind for which the policy is unclear.

Questions have been asked before about what constitutes a duplicate, but what was interesting (well, I thought so) about this duplicate was that my question was narrow in scope, and the question it was closed as a duplicate of was broad in scope. An answer to my question was buried in the answers of the original question, but not at all easy to find.

Does the policy about duplicates need clarification about "broad" and "narrow" questions?

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  • Why do we need to change the policy? Why can't close and re-open votes cast by the community take care of this "problem"?
    – Cody Gray
    Apr 25 '12 at 20:07
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    @TheEstablishment The policy as people understand it is evidently not as clear as you think.
    – Raedwald
    Apr 26 '12 at 9:31
  • @Raedwald - Actually I think it's worked perfectly here - a borderline case has been handled entirely by the community and reached a state that looks like consensus, without moderator intervention.
    – Flexo
    Apr 26 '12 at 12:23

If the best answers to the question already exist then duplicating them introduces what amounts to update anomaly and diminishes the long term usefulness of both questions by spreading the knowledge between them.

So long as a question closed as duplicate isn't deleted then it still serves to help others find the question with the canonical answers. (Automatic redirects for questions closed as duplicates with no answers might help avoid the "clicking chains of dupes" problem. There's several questions on that already: Q1, Q2 Q3, it seems this was added recently for anonymous users)

That said in this instance I don't think a copy and pasted answer from the other question would work - there's no mention of SSO in the other question, so dupe seems inappropriate as things stand.

  • Well the accepted answer of the explained does explain SSO just fine imo, but: I think a good SO answer should be succinct and only contain as much information as necessary to answer the question. That's clearly not the case here, so I think it warrants a new answer.
    – Voo
    Apr 25 '12 at 16:28
  • I pressed Ctrl-F and typed SSO and the only match was on a comment that was added very recently. At the bare minimum an edit would have been helpful.
    – Flexo
    Apr 25 '12 at 16:30
  • It doesn't mention the acronym but it does explain "short string optimization". So I think coming from the "what is SSO" question to the answer wouldn't confound any reader. Just to be clear: I completely do agree with you that I wouldn't consider the answer good for the question "What is SSO".
    – Voo
    Apr 25 '12 at 16:33

In a related Meta question, Jalf gave an answer quoting a blog post by Joel, which is highly pertinent (emphasis added):

If you’re going to close a user’s question as a duplicate, it has to be a real duplicate. For example, if a user asks, “What does the IP address mean?” it’s OK to close that as a duplicate of a more general question like “What do IP addresses of the form a.b.c.d/e mean?” But it’s not OK to close it as a duplicate of a twenty-seven page guide to netmasks. That’s the moral equivalent of saying “RTFM.” Stack Overflow is not meant to be a library of reference manuals. It’s supposed to contain the same information as a library of reference manuals, in the form of millions of questions and answers. Combined with Google, that gives us the magical power of a library of reference manuals you never have to read! It’s like, you got to the library, and there’s a wizard there at the door, and you ask your question, and, instead of being told to read a book, you just got (are you sitting down?) the actual answer!

Joel seems to be saying that, no, narrow questions should not be considered duplicates of broad questions. And I see his point: all C++ questions can be reduced to duplicates of "how do I program in C++".

  • There are cases where narrow questions ought to be closed as duplicates of more general question (e.g. the infinite variations on i = i++ + ++i being closed as duplicates of the question on UB and sequence points). The other option of course would be "too localised" but that's monumentally unhelpful.
    – Flexo
    Apr 26 '12 at 12:30

The explanation of "exact duplicate" is

This question covers exactly the same ground as earlier questions on this topic; its answers may be merged with another identical question.

In some cases, there may not be a clear-cut answer as to whether one question is an exact duplicate of another. For this reason:

  • Questions are closed as "possible duplicates" with links to the other question.
  • Closing a duplicate requires five votes from users with 3k+ reputation (users smart/experienced enough to know whether it is actually a duplicate), or one vote by a mod (users trusted to make such decisions).
  • Closed questions can be reopened. If 5 people say "this is a duplicate" and close it, and 5 more people say "no, it's not, because it is different in this way", then it's reopened

It's ultimately a subjective decision, which can be reversed.

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