Coping with *abstract* duplicate questions.

Question

Any longtime reader cannot help but notice that we get many abstract duplicate questions, e.g. this recent question on partial fraction computation, which is not essentially different from many other questions of the same shape, e.g. this question. Once you know how to solve one of these problems you can solve them all. There are many classes of problems that frequently arise in reparametrized variants, e.g. divisibility problems using Fermat's little theorem, proving basic properties of gcds, etc. Does it make sense to try to try to prevent these minor variations from swamping the site? In a couple years time we could well have many hundreds of variants of such questions that are all essentially the same except for minor variation of parameters. Among other detrimental consequences, this greatly obfuscates search results. Certainly our user community has the expertise to appropriately classify and eliminate these "abstract" duplicates. Perhaps with a little ad-hoc add-on infrastructure, and with moderator support, we could address these issues before they get out of hand. Thoughts?

Answer 1

The current thinking is that subtly different variants of the same question be closed as duplicates of a more canonical, more general question and answer pair:

http://blog.stackoverflow.com/2011/01/the-wikipedia-of-long-tail-programming-questions/

If you keep seeing the same form of questions, whether it’s mod_rewrite rules on Server Fault, freezing computers on Super User, or how to use regular expressions to parse HTML, write a great, canonical answer, once and for all. Make it community wiki so that as many other people as possible can make it great. Work really hard on writing something that is clear, concise, and understandable by as wide an audience as possible.

Personally, I would express this sentiment as "old-timers are tired of answering what is essentially the same question in millions of tiny different varations".

Whenever you feel that is happening, I recommend approaching it as per the above.

Answer 2

I would suggest that:

• if there is a sufficiently-general form of the question, new variants should be closed as duplicate, but not deleted—this provides a way for someone searching for that variant to get to the more general result;
• if there is not a sufficiently-general form of the question, ask the general form of the question so that it can be answered in the general case (remember, you're allowed to ask and answer your own question as doing so provides valuable content) and future variants can be closed as duplicates, as above.

Answer 3

(too long for comment)

I agree. It is not clear what should be done. Sometimes the problem can be fixed if the most general solution was posted. As an example, the following three threads are conceptually identical:

Limit of $\lim_{x \to\infty} 3\left(\sqrt{\strut x}\sqrt{\strut x-3}-x+2\right)$

Limit of algebraic function avoiding l'Hopital's rule

Limit of algebraic function $\ \lim_{x\to\infty} \sqrt[5]{x^5 - 3x^4 + 17} - x$

But here, the question can be generalized and solved. That is for polynomials we can show: $$\lim_{x\rightarrow\infty}\sqrt[n]{x^{n}+a_{n-1}x^{n-1}+\cdots+a_{1}x+a_{0}}-x=\frac{a_{n-1}}{n}$$

Should they be merged? I definitely think so. The proof techniques in the answers of each post are exactly the same.

A harder question is what to do with all the Fermat's little theorem problems They are all so similar, but different enough that there is no "universal case" that can be proven.

Answer 4

A request for comment:

Perhaps it will be worthwhile to have a two-pronged approach:

• Maintain a list of FAQ This is not an FAQ in the sense of how to use the site. But actually a list of Frequently Asked Questions. This could be implemented as a Meta Thread (and to be incorporated in/linked to from the FAQ on how to use this website), or perhaps as a tag (though for the latter it'd be much more reasonable for this to be a "restricted" tag, with a reputation limit before one can tag a question as such). To this list (or a separate one) we can also add all those silly puzzle questions that crop up every now and then, and those inevitable questions about 0.999999... = 1.
• Aggressively closing and possibly deleting such minor variants and duplicates. If I am not mistaken, 10K+ users (of which there are quite a few now on this site) can vote to have an already closed question deleted. So with a bit of help from the community we can certainly clean up the clutter.

To populate the list of FAQ, each question in the FAQ should be a good CW, abstract question/answer to a canonical form of the question that often appears. And ideally we should also link to, in that question should be included links to some less abstract examples that has already appeared on this forum. So we address the abstract and the practical in one go.

Of course, this will require a lot of work from the community.

Answer 5

At least so far, I don't see this as a problem. It would be nice if a search turned up the earlier variants, but I don't know how to do that and the evidence is that the posters of these problems don't search anyway. I would support a relaxation of the wording of "exact duplicate" to "if you read this you should be able to figure it out", but the volume is not too bad. If I can find the previous answer I post a link, but often I can't.

Answer 6

I don't know what the moderator features are on the site, but it might be possible to merge the specific questions into the thread of the more general one under a category of "examples".

Answer 7

One of the reasons we get the same question over and over is people who are learning new concepts cannot tell if two problems are essentially the same. In a sense, what they are asking us is "what type of problem is this and how do I know it is that type?"

Deleting what looks, to trained eyes, to be "minor" variations will not stem the flow of questions... but grouping a large number of similar examples together just might.

Is there any way that we could do this?