I propose adding n cat lab tag with an intention to discuss mathematics that is written in https://ncatlab.org/nlab/show/HomePage.

As https://ncatlab.org/nlab/show/HomePage has large amount of mathematics used as reference and/or as in learning for the first time I guess it would be useful to have a tag.

Questions in this tag should be restricted to mathematics written there.

This is not just to attract attention of editors of n Lab.

In that case it might be easier to bring to the notice of some one who has written something there if there is any problem. This is with an assumption that, author of that page is in MO. I am aware of one of the authors namely Urs Schreiber is a member of MO. It is very unlikely that author would respond to a mail sent by some one (unless that some one already familiar). So, this would be useful for betterment of users who use that site.

I would really want to add tag of n-lab for at least two of my questions Composition of bibundles and In what sense bibundles are called as generalized morphisms.

What does the MO community think about this?

  • $\begingroup$ Downvote for what reason? $\endgroup$ Commented Jun 30, 2018 at 8:52
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    $\begingroup$ Do we have a tag for Wikipedia? $\endgroup$
    – Asaf Karagila Mod
    Commented Jun 30, 2018 at 11:08
  • $\begingroup$ @AsafKaragila I guess wikipedia is not at all comparable with nlab... anyone can edit in wikipedia, where as one can not do the same in case of nlab... $\endgroup$ Commented Jun 30, 2018 at 11:09
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    $\begingroup$ There are a number of assumptions here which are questionable, for example that there are restrictions on who can edit the nLab, or that MO is the best way to reach an nLab editor. Of course you are free to ask mathematical questions about nLab content at MO, and people frequently do this, but if what you really want is to reach an nLab author, then you should write to the nForum instead. $\endgroup$
    – Todd Trimble Mod
    Commented Jun 30, 2018 at 11:32
  • $\begingroup$ @ToddTrimble reaching n lab editor is not the only goal, if that is what my question sounds like.. I mean there is a possibility that nlab editors might see that. Are you saying " there are restrictions on who can edit the nLab," is not correct? $\endgroup$ Commented Jun 30, 2018 at 11:56
  • $\begingroup$ Yes, that's what I'm saying. Of course people who post spam or nonsense may be blocked and have contributions removed, and "we" at the nLab strongly urge serious contributors to announce their edits at the nForum except for trivial cases like fixing typos. $\endgroup$
    – Todd Trimble Mod
    Commented Jun 30, 2018 at 12:37
  • $\begingroup$ @ToddTrimble I know that you are also involved in nlab :) Are you saying a tag for nlab is not a good thing here? $\endgroup$ Commented Jun 30, 2018 at 12:55
  • $\begingroup$ I'm undecided about the tag. $\endgroup$
    – Todd Trimble Mod
    Commented Jun 30, 2018 at 13:08
  • $\begingroup$ @ToddTrimble I can understand that :) $\endgroup$ Commented Jun 30, 2018 at 13:23
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    $\begingroup$ @PraphullaKoushik I would rather tag a question by topic than by origin, so I don't see the ncatlab tag as particularly helpful. It's like having tags for the names of famous mathematicians: sure, you might like to discuss something you found in one of Hartshorne's book, but do you really want to tag the question hartshorne? $\endgroup$ Commented Jul 4, 2018 at 8:16

1 Answer 1


If there were an agreement between parties at both nLab and MathOverflow involved to share administration, editorial, and other duties, so that questions about one system were welcome at the other, then I would see the use in such a tag.

At present (from my remote and partly ignorant perspective of the nLab) the two systems do similar things but in different fashions. They both serve mathematical communities with material at or near research level, but they have different methods and different philosophies. In particular, nLab does not do Q and A (although some of their chat fora might) and MathOverflow is not intended to produce overview articles or exposition on broad areas, or even narrow areas, of mathematics. (It does do exposition for specific questions within narrow areas.)

The current reasons suggested seem to me to be of limited convenience for both the nLab and MathOverflow communities. If you can provide more examples about how both communities can benefit (right now it appears to me to be more and inappropriate advertising for nLab), I may change my opinion about the tag's suitability.

Gerhard "ArXIv Tag Is Quite Different" Paseman, 2018.06.30.

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    $\begingroup$ “to share administration, editorial, and other duties,” :O I am surprised to see this reply... I did not say anything that looks atleast closer to this.. Did I?? $\endgroup$ Commented Jun 30, 2018 at 15:36
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    $\begingroup$ I do not see how second paragraph is related to my question :O I was just asking to put a tag so that people can relate with what I saw/I know and what I am asking... $\endgroup$ Commented Jun 30, 2018 at 15:38
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    $\begingroup$ Discussing stuff that appears at the nLab may be your intention. That is not how others will see it. Others will see it as talking about nLab itself. If nLab became part of the MSC, I might see a reason for it. Tagging by forum name does not make sense to me. Gerhard "That's How I See It" Paseman, 2018.06.30. $\endgroup$ Commented Jun 30, 2018 at 15:45
  • $\begingroup$ Oh.. no problem.. :) discussing stuff that appears at the nLab is my intention... that’s up to moderators.. I do not know how to convince more than this,.. $\endgroup$ Commented Jun 30, 2018 at 15:53
  • $\begingroup$ The purpose of the second paragraph is to suggest why even given conditions from the first paragraph, the two systems are different, and that drawing such an association between them with a tag (and other ties) might end up being a bad idea. Gerhard "Again Is Seeing It Differently" Paseman, 2018.06.30. $\endgroup$ Commented Jun 30, 2018 at 16:20
  • $\begingroup$ Fine... I give it up here... thanks.. $\endgroup$ Commented Jun 30, 2018 at 16:37

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