# Tag management 2020

New year, new tag management thread.

Rules of the game are basically the same:

• Post your suggestion as an answer here if you see
• A particularly bad tag (a rule of thumb: “if I can't imagine a person classifying a tag as either interesting or ignored, I'm getting rid of it”),
• A tag that should be a synonym of an existing one,
• A tag that used for two or more completely unrelated things,
• A need to create a new tag.
• Upvote/downvote/comment as your agree/disagree with suggestions, so please post different suggestions in separate answers.
• Wait a couple of days before implementing a suggestion.
• After the problem described in an answer is resolved, please edit it to say so.
• If your tag suggestion exists in a separate question, please provide a link to the question in your suggestion.

Also, note that one may use [tag:calculus] for , i.e. tags on the main site, and [meta-tag:discussion] for , i.e. for tags on the meta site.

• Even though we have a tag management thread, it's worth pointing out that in some cases it might be better to have a separate question. (Typically when a longer discussion is needed and several possible answers are expected. Answers to a question provide more space for a more detailed discussion than comments under an answer in this thread.) – Martin Sleziak Jan 6 at 1:19

# Proposal: epsilon-delta$$\rightarrow$$limit-definition

Following a suggestion posted here as a comment, I suggest that we rename the epsilon-delta tag as and that becomes a synonym for that tag.

• At first I thought this is a good idea. Yet if somebody would ask something like: "Use the epsilon-delta definition of continuity to prove directly that $x \mapsto x^2$ is a continuous function on $\mathbb{R}$." then the former seems natural as tag yet the latter maybe not so much. Thus, I am now a bit on the fence about this. – quid Apr 24 at 10:02

Proposal: Create tag xor

xor, also known as symmetric difference, is a logical operator for which we have no separate name in English -- for example, when we say "do you want ice cream, or do you want cake", we mean xor but we say or. Since for many people, this is the first new logical operator they learn (since they already understand and, or, and not), various issues therefore arise. These range from:

• Explain how xor works.

• How do you xor with 3 or more items (saying "Do you want ice cream, cake, or pudding?" means choose 1, but in xor of three items, you either choose one, or you take all three -- but not just two).

• How do you phrase xor best when writing (many notations exist).

• Understanding bit-wise xor in computer science.

• Expressing xor in terms of more simple operators.

I could go on. Questions regarding xor itself.

There are hundreds of posts asking about properties of xor and how it works, many of them with a single tag of boolean-algebra or logic or propositional-calculus. I believe it deserves its own tag.

I didn't know we had to get approval for this in advance, so I already re-tagged some questions; but, I'd be willing to undo my edits if we decided not to add it.

• I don't think this is a particularly useful tag. Searching for XOR will lead you to the questions about XOR. So it has no particular value in helping search and classify questions about XOR. It also sets a precedent for tags for other logical operators (which in that case, should just be the one tag logical-operators or some variant thereof). – Asaf Karagila Sep 27 at 12:33
• I'm not sure why you say xor is not associative. It certainly is. – Matt Samuel Sep 27 at 13:19
• @MattSamuel Thanks, the reason I was thinking turned out a little more nuanced. – Alex Sep 27 at 13:26
• I would also refrain from creating a new tag and immediately going on a retagging spree while applying it to a bunch of questions. If it doesn't merit community approval, you've done a lot of unnecessary work, and doing so may replace a relevant fifth tag. – Integrand Sep 28 at 2:01
• Just a small reminder: in case you decide to undo the edits, make sure you do it slowly so that the home page won't be flooded with those questions. – YuiTo Cheng Sep 28 at 11:52

Proposal: Merge and tags.

The idea behind having two tags is to divide basic and advanced probability questions, but it does not work and I believe it couldn't work. It is better to have single tag and use additional tags like , , etc.

PS: Downvotes show that is like a suitcase without a handle: hard to carry but a pity to throw away.

• Older related posts: About [probability-theory] tag and The tags (probability) and (probability-theory). As you said, both tag-info and a related comment template suggest to keep them separate. I have tried to summarize this also in the tagging chatroom. – Martin Sleziak Jan 8 at 7:24
• Regarding the recent edit, it is probably possible to maintain a pair of such tags - but for that some users who will follow the tag will be needed. For example, (elementary-set-theory) and (set-theory) are in quite good shape since there are users who follow them very closely and retag the questions when needed. – Martin Sleziak Jan 9 at 8:44
• Do you think that renaming the tag to (elementary-probability) would it make more likely that people would be using the tags correctly (i.e., in the way they are described in the tag info)? Currently (elementary-probability) is a synonym of probability, with (probability) as the master tag. – Martin Sleziak Jan 9 at 8:46
• @MartinSleziak I don't think that retaging questions by other users is good idea; also I don't think that the current status of probability-theory tag as an alternative to probability tag is a good idea; anyway, it does not work in practice. I think probability-theory can be used either as a secondary tag for the main probability tag, or simply removed. And there is no need in elementary-probability tag. – kludg Jan 9 at 9:37
• Elementary probability problems and more advanced probabilistic concepts should definitely not be merged. These are handled very differently and require very different levels of mathematical knowledge. As an analogy: imagine if we merged number-theory and elementary-number-theory – what a disaster that would be! – URL Jan 9 at 19:21
• @URL How this is related to the particular probability and probability-theory situation? In no way. I believe most downvoters rarely or never visit probability questions, and don't understand why probability-theory tag is not needed. – kludg Feb 20 at 15:42
• I wouldn't merge them, but renaming probabilty as elementary-probability seems to be a good idea. After all, it states "For basic questions about probability [...]". – Jean-Claude Arbaut May 5 at 7:35