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12:08 PM
For the three most recent instances, it seems to me that "general topology" was an acceptable replacement. Off-hand, my feeling is that there's not much of a danger: in the (probably) rare cases where "general topology" was a misnomer, the tag could be edited on an ad hoc basis. — Todd Trimble ♦ 17 mins ago
2 hours later…
1:58 PM
I have to admit that on math.SE there is this synonym and I do not recall some major problem. If (topology) becomes synonym of (gn.general-topology), this will be a slightly different situation from the situation when (topology) was a separate tag. If somebody types "topology" in the tag field, they are shown the tag excerpt. (But I have seen a fair share of badly mistagged question, so it is clear that many users do not pay attention to tag-excerpts. Probably MO regulars can say whether the situation on this site is better.) — Martin Sleziak 27 secs ago
2:51 PM
@MartinSleziak I am really not a topologist but "general topology" in addtion to "algebraic topology" for the following question seems not suitable.
Q: A relation between the index of a fundamental group and the covering map

e.turattiMy professor just enunciated this statement: $|\pi_1(X,x_0):\pi_1(\tilde X,\tilde x_0)|=\#P^{-1}(x_0)$ where $P$ is the covering $P:\tilde X\rightarrow X$, such that $P(\tilde x_0)=x_0$. I've tried for hours to prove this, but I can't get it done. I would appreciate any help. Thanks in advan...

This one is maybe less clear but:
Q: CW complex= cell complex?; compact metrizable spaces

ms.mopI have a question about finite cell complexes and compact metrizable spaces. In a paper I read the statement: Let $X$ be a compact metrizable space. Then $X$ is a countable inverse limit $\varprojlim\limits_{i\in \mathbb{N}} X_i$ of finite cell complexes. My questions: 1)What is meant by ce...

I am not saying that everything is perfect. But you would find mistagged questions in almost any tag.
Yes, but I found these two among the last 10.
This might be consequence of the synonym. But it also can be mistake by OP or an editor not cause by this.
Or is there some way to see which questions where tagged (general-topology) using the tag synonym (topology)?
Indeed, it is impossible to know if the automatic retag was at work AFAIK, which is one of the problems with having a synonym.
The number is known.
Yes, but that is the total number where the synonym was used or remapped or whatever is the correct term.
We do not know just from the number whether they were tagged correctly or not.
2:56 PM
The manual retaging in case of errors would be a lot harder, as one would have to sift through all question in the master tag.
We can may an educated guess that the synonym is likely to contribute to incorrectly tagged question. But it is difficult to quantify how many questions have been influenced by this.
@quid I agree, but this is definitely a lesser problem at MO than at MSE. MathOverflow has how many question per day? 50? Or maybe 100?
Yes. But the real question is what is gained by having that synonym.
@MartinSleziak 30 - 40 q. Yet, no it is not a lesser problem. Because there is virtually no one that cares. You saw how long it took until the toplogy tag was noticed.
But if the issues related to tags are regularly brought up on meta, there will be more users who will try to improve tagging.
I guess that after my recent post a few more users know about deprecated tags.
Well. I really do not care that much. But I might propose the synonym on Mathematics is cancelled.
Still even if you say that synonym causes problem, I'd hope that you agree that the situation with synonym is better than situation with a standalone tag. (Which was the first part of might comment.)
3:03 PM
No, not at all.
My argument was that the tags behave differently for a synonym than for a standalone tag when entered in the tag field.
Typo: might comment $\to$ my comment.
It is not clear to me how that would help that much.
Again, it is a mystery to me what the synonym should achieve.
Well, at least I thought that the user is more likely to notice it because they see two things: tag-excerpt and the master tag is shown there.
But on the other hand you are right that users often ignored tag-excerpt saying that a tag is deprecated.
At least that was my experience from math.SE with (abstract-algebra). I cannot judge whether it was the same here with (topology) and (geometry).
3:09 PM
Ok. You have certainly some good arguments. I am going to delete my comment.
However, from the MathOverflow POV I did all I could. I brought up the issue on meta. And I posted also an answer pointing out possible problems with a synonym.
Perhaps the fact that the same synonym exists at MSE could be useful, if there was a way to find out to which extent that synonym contributed to incorrectly tagged questions.
From Math.SE POV - I will certainly glad if you post the suggestion what to do with the (topology) $\to$ (general-topology) synonym on that site, together with your arguments.
On the MO and math.SE comparison, one could imagine that it will be more of a problem on MO as there are relatively more non-general topology questions.
That seems to be true. On math.SE (general-topology) tag is much bigger than (algebraic-topology). On MO it is the other way round.
3:24 PM
Yes, this may be an argument why the syn makes some limited sense on math.SE General is twice as large as all others combined.
But on MO it is not only much smaller than AT but also smaller then geoemtric toplogy.
To me it seems a nobrainer one should either leave things as they are (that is "kill manually" when it reappears) or blacklist.
You mean here on MO. But from what you wrote above, it seems that you probably prefer the same solution on MSE, right?
3:55 PM
@quid In fact has 2040 questions and has 1961 questions. In the tag-list the numbers are shown separately for the master tag and the synonym . But still, these two tags are comparable and much smaller than .
4:11 PM
BTW I have edited my answer - I have mentioned the synonym on MSE; and also the fact that the biggest topology-related tag is different on MO than on MSE.
@MartinSleziak thanks for the correction, I missed that. On math.SE I feel this list of dually tagged questions shows quite a few where general-topology seem not suitable to me. But you are better place to judge.
I should probably try to work more on correct tagging on MSE (where I have full edit privileges and I know the tag system better) than on MO. But I hope that I'll come to MO more often than I used. And if I am not able to help by writing good answers, some copyediting or retagging is IMHO a useful thing to do, too.
I am not entirely sure whether I will be a good judge on the questions from that list, since I know very little about algebraic topology. It is not always clear-cut whether the question belongs to general topology tag or not. And sometimes understanding algebraic topology might be useful to make the decision.
Yes, it's certainly useful. If it were nor for you, who knows for how long that topology tag had regrown.
Well, it was created on June 9th. So it was less than a month before it was discussed on meta and removed. Admittedly, we cannot be sure whether somebody else would have notice.
But even if there are occasionally problematic tags, such as and , my guess is that the fact the the tags follow to some extent arxiv classification makes the tag-maintenance here on MO a bit easier than on math.SE.
I prefer not to comment on that subject. :-)

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