derivation tag removed

This is not a big deal and I don't mind however it turns out, but I mildly object to the removal of the "derivation" tag from my question here: https://math.stackexchange.com/posts/953057/revisions

Apparently the tag was previously deleted based on the colloquial meaning (eg., "deriving a formula") being too vague for a tag.

However, my question is about generalizing the Leibniz rule, so the meaning of the tag is in the technical sense of derivations (an algebraic generalization of the derivative based on the Leibniz rule), rather than derivation in the colloquial sense.

So, the question for discussion is: should we allow the "derivation" tag to be used when it is done in the specific technical sense, or is the potential for misuse so high that it should be banned regardless of the context?

I would like to point out that there exist numerous tags that have a colloquial and technical meaning, but are used here only in the technical sense - for example,

• analysis (meaning breaking a complicated topic into pieces to understand it) vs. analysis the mathematical field of study

• function (an action that a system can perform), vs function (a mapping between sets).

and so forth. If you just browse the front page, a substantial fraction of all tags have a double meaning like this.

• There is a saying that it's easier to apologize later than get permission first. I disagree with that when it comes to new tags. When I see a new tag which wasn't discussed on meta first, I will almost always delete it. Especially if I wouldn't be 168% sure that I'd agree with having that tag on the site. – Asaf Karagila Oct 2 '14 at 4:36
• Since you chose these two tags as examples, it is worth mentioning that removal of both analysis and functions have been discussed on meta. – Martin Sleziak Oct 2 '14 at 6:18
• I wanted to make sure that you are aware of the (differential-algebra), which also seems appropriate for this kind of questions. – Martin Sleziak Oct 2 '14 at 7:22

Tags named after mathematical objects or concepts are generally less useful than tags representing areas of mathematics. They may be even harmful, when users pick them instead of the area tags. I think is an example of such scenario: it could be replaced by on every occasion (they often go together, but not always). As a result of this tag existing, some linear algebra questions are not classified as .

Another obstacle is that "derivation" also means the process of deriving something, and the users who only know the word in this sense greatly outnumber the users who know the other meaning, or bother to read the tag wiki. Consider what happened to .

(The fact that some words used in tags have non-mathematical meanings is less of a problem, since this is evidently a site for Mathematics, and questions tends to be mathematical.)

The tag for derivations in the sense of differential algebra should be created, but it should be made clear already in the tag-name, what is the purpose of this tag.

For example would fit 25 character limit for tag-names. (If you have better idea for an appropriate tag-name, feel free to edit the post or make a suggestion in the comments.)

Please upvote/downvote this post to show whether you agree/disagree with this.

• I was also considering (derivations-algebra) as a suggestion for the tag name, but such name still feels too ambiguous. – Martin Sleziak Oct 2 '14 at 7:28
• Maybe (derivations-coderivations) (if this happens)? It should make clear what it means, and include another very closely related thing. – Najib Idrissi Oct 2 '14 at 8:06
• I like this. Even if some people still use it inappropriately on their own questions out of confusion (that is inevitable for many good tags), it would be easier for others to spot the need to retag. – Jonas Meyer Oct 2 '14 at 12:50

For new tags, especially in the cases where the name might be ambiguous, it is important to explain usage of the tag in the tag-info (tag-excerpt and tag-wiki). So in case the result of this discussion is that some tag for questions about derivations in the sense of differential algebra is created, we should make at least some suggestion what the tag-info should look like.

I have made this post CW, if you have some ideas how to improve tag-excerpt and tag-wiki, please, edit this post.

Proposed tag-excerpt:

This tag is for questions about derivations in the sense of differential algebra. Do not use this tag for questions dealing simply with deriving some fact/formula/result from another.

Proposed tag-wiki:

This tag is for questions about derivations in the sense of differential algebra. Do not use this tag for questions dealing simply with deriving some fact/formula/result from another.

Derivation is a function on an algebra which generalizes the notion of derivative. If $A$ is an algebra over a ring $K$, then a function $D\colon A\to A$ which is $K$-linear and satisfies Leibniz's law $D(ab) = (Da)b + a(Db)$ is called a derivation.

• Originally I have posted this as a part of one of the "poll answers" on possible tag-name. But perhaps it is better to keep the discussion about the tag-wiki separate. (Of course, this will only be needed if the tag is created.) – Martin Sleziak Oct 2 '14 at 7:38

The tag for derivations in the sense of differential algebra should be created, but it should be made clear in the tag-info (tag-wiki and tag-excerpt), what is the purpose of this tag.

Please upvote/downvote this post to show whether you agree/disagree with this.