Tagging - 2017-09-03

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5:47 AM

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Q: The first "class": calculus, with Simply Beautiful Art

Previous meta posts for background: Discussion groups to assist those self-studying or enrolled students A call for volunteers - "study group" coordinators and advisors Class SimplyBeautifulArt has kindly volunteered to guide our first "class", on calculus! It will be a basic calculus cour...

discussion

Can we perhaps not turn the meta site to announcements and polls about this project? — Asaf Karagila 2 hours ago

In relation to @Asaf's comment, I'll ask whether somebody could think of a suitable name for a tag related to "this type" of posts. (In this way, people who are not interested could at least avoid posts about this project by adding it to ignored tags.) — Martin Sleziak 35 mins ago

7 hours later…

Martin Sleziak

12:33 PM

specific-question I see that in Prove: Suppose $\alpha > 1$ and $\beta, \gamma$ are ordinals with $\beta < \gamma$. Then $\alpha^\beta < \alpha^\gamma$. the tag elementary-set-theory was change to set-theory. OTOH ordinal and cardinal arithmetic is explicitly listed in the elementary-set-theory tag-info.

Q: Prove: Suppose $\alpha > 1$ and $\beta, \gamma$ are ordinals with $\beta < \gamma$. Then $\alpha^\beta < \alpha^\gamma$.

In this question, $\alpha$, $\beta$ and $\gamma$ are ordinals. I want to prove this by transfinite induction on $\gamma$, which typically has two or three cases. I'm considering three cases: the base case ($\gamma = 0$), the successor case ($\gamma = \delta + 1$) and the limit case. I was strugg...

set-theory ordinals

@Martin We have been fairly actively keeping the two tags "set theory" and "elementary set theory" disjoint. — Andrés E. Caicedo 5 mins ago

@AndrésE.Caicedo Fair enough, but if you look at the tag-info, ordinal arithmetic is explicitly listed under (elementary-set-theory). Anyway, since this is not really related to this specific question, I would suggest to continue this discussion either in chat or on meta. — Martin Sleziak 23 secs ago

@Martin It's been the practice for years. I do not participate in chat, and try to avoid commenting in meta unless essential. Thank you. — Andrés E. Caicedo 12 secs ago

@AndrésE.Caicedo I have retagged the question once again to comply with the description in the tag-info. (In fact, the tag-info has included ordinals this way for a long time.) But I definitely will retag question again if you change it to (set-theory) - I am well aware that you and Asaf basically curate these two tags. (Still, I think that it might be reasonable to open discussion on meta about this, if the usage is unclear.) — Martin Sleziak 25 secs ago

I am not sure whether you will read this, but anyway.

Basically it was unclear to me whether you objected to the fact both these tags are used simultaneously or whether you think that ordinals belong to (elementary-set-theory) tag rather than (set-theory) tag.

Martin Sleziak

1:20 PM

Sorry, I wanted to write: "...or whether you think that ordinals belong to (set-theory) tag rather than (elementary-set-theory) tag".

I see that Andres E. Caicedo now edited the tag-info and removed the part: "transfinite induction, well-orders, ordinal and cardinal arithmetic, ..."

So at the moment the tag-wiki reads:

> This tag is for elementary questions on set theory, focusing on material usually covered in undergraduate set theory texts. More advanced topics should use the tag set-theory instead. Topics include intersections and unions, de Morgan's laws, Venn diagrams, relations, functions, countability and uncountability, power sets, etc.

The tag-excerpt was not changed:

> This tag is for elementary questions on set theory, spanning topics usually found in introductory courses in set theory, in addition to review sections of graduate textbooks in the same field. Topics include intersections and unions, differences and complements, de Morgan's laws, Venn diagrams, relations, etc. More advanced topics should use the "set-theory" tag instead.

@AndrésE.Caicedo Sorry for pinging you once again. What I wanted to write in previous comment was that "I definitely will not retag the question again" if you change the tags back to your choice. (The fact that I've forgotten the word "not" changes the meaning substantially. I posted the comment mainly to make clear that I do not want to start editing/retagging war.) I have noticed that you have edited the tag-info. we will see whether people will change how they tag the questions after the tag-wiki was changed. — Martin Sleziak 8 secs ago

This is only the rough estimate (since we would have to examine the questions more closely) but currently there are 416 questions tagged ordinals+set-theory and 296 questions tagged ordinals+elementary-set-theory.

Martin Sleziak

1:43 PM

I see that the above comments have been already removed from the main site. Moderators are fast. :-)

Martin Sleziak

2:06 PM

@Martin Thank you, and thanks for pointing out the typo. — Andrés E. Caicedo 2 mins ago

The question was retagged back to set-theory. At the moment, I am not sure whether it is necessary to bring up on meta whether ordinals (or at least basic questions about ordinals) belong into (elementary-set-theory) or into (set-theory) tag.

I'll try to watch how Asaf and Andres tag such questions - they are among the most active users in those two tags. (And certainly the most active as far as tagging and retagging is concerned.)

10 hours later…

Martin Sleziak

11:47 PM

@MartinSleziak suggestion for tag that could help via favorites/ignores: chat-event, which is both what some other sites use to organize their chat events and the name for the SE chat feature implicated. — nitsua60 26 mins ago

What do you think of chat-event? Or do we have something more fitting?

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