Wikipedia:Articles for deletion/Proofs involving the Moore–Penrose inverse


 * The following discussion is an archived debate of the proposed deletion of the article below. Please do not modify it. Subsequent comments should be made on the appropriate discussion page (such as the article's talk page or in a deletion review).  No further edits should be made to this page.

The result was delete. There's a rather broad community consensus that Wikipedia is not a textbook, and the "keep" opinions must accordingly be given less weight.  Sandstein  10:00, 21 February 2022 (UTC)

Proofs involving the Moore–Penrose inverse

 * – ( View AfD View log | edits since nomination)

This article blatantly violates WP:NOTTEXTBOOK, as it develops content from initial lemmas to propositions just as a textbook would, rather than like an encyclopedia. Since it is actually quite well written, I transwikied it, reformatted it, added some explanations and exercises and added it to a textbook on Wikibooks, where it fits much better. Felix QW (talk) 14:59, 6 February 2022 (UTC)
 * Note: This discussion has been included in the list of Mathematics-related deletion discussions. Felix QW (talk) 14:59, 6 February 2022 (UTC)
 * For more background, note this discussion: "Proofs_involving..." articles.--RainerBlome (talk) 01:32, 10 February 2022 (UTC)
 * As the material has already been transwikied to a more appropriate place, all that's left is the tidying-up. Delete unless a redirect needs to be kept around to preserve the page history for attribution purposes. XOR&#39;easter (talk) 23:01, 9 February 2022 (UTC)
 * As I used official import procedures, the page history has been transferred too. Conserving attribution here is therefore not necessary for attribution purposes. Felix QW (talk) 08:23, 10 February 2022 (UTC)
 * Thanks for clarifying. XOR&#39;easter (talk) 21:03, 10 February 2022 (UTC)
 * As far as I understand, the idea of the proposal is not to nuke content, but to move it. Cool URIs don't change, so iff the decision should be to move, I'd suggest a Soft redirect instead of a delete, to keep incoming links working. It would look like this: .--RainerBlome (talk) 00:18, 11 February 2022 (UTC)
 * Oppose, because it would make the world worse.


 * Even if the proof page can be seen to violate WP:NOTTEXTBOOK, it should stay. I invoke the Wikipedia principle WP:Common sense.


 * Following the "common sense" flow chart:


 * -> Does the proof page improve the encyclopedia? Yes. I think the proof page fits well in Wikipedia, because it complements the article page. This is no surprise, because the proof page's purpose is to support the article (and not to serve as a textbook). I think it is a good idea to keep wiki proofs close to the material that they support. In particular, this keeps the interested editorship close to the proof page.[1]


 * -> Does it break the rules? Yes.[2]


 * -> Is that because the rules are wrong? No, the rules are fine.


 * -> Ignore the rules and DO IT


 * In this case, "DO IT" means to do nothing, leave the page in place. Sometimes, it is better to do nothing. But let's discuss, discussing this is good.


 * [1] When I look at the other pages in the wikibook "Topics in Linear Algebra", I see far less edits. I fear the content would wither and die on wikibooks. On Wikipedia, 72 editors have contributed 341 edits. (https://xtools.wmflabs.org/articleinfo/en.wikipedia.org/Proofs_involving_the_Moore%E2%80%93Penrose_inverse) Even though the topic of the proof page is very narrow (compared to, for example "Field theory" (https://en.wikibooks.org/wiki/Topics_in_Abstract_Algebra/Field_theory), the proof page is currently the longest page in that book. Had the page been created at wikibooks in the first place, it would not be at the current level of quality.


 * [2] The proof page has many proofs, develops them from each other. It shares this property with a textbook. But it is not a textbook, it is not intended to be a textbook. The "Proofs involving" discussion linked to above mentions that the proof page was originally a subpage, and was promoted to "article" only because subpages are no longer allowed in article namespace. As such, the proof page is conceptually still a sub-page, a supplement to the article, intended to make the article more easily verifiable. One of the reasons for the page's existence is that for these proofs, literature is somewhat hard to get a hand on in practice, simply because it is a bit of a niche topic. The page indeed provides an alternative to such other literature. As does all of Wikipedia, in a sense.


 * It has been claimed that the wikibook would be a more appropriate place. For what reason? The other topics are more "abstract algebra", while the proof page is intended to support an article mostly about concrete algebra (matrix algebra).


 * --RainerBlome (talk) 01:13, 10 February 2022 (UTC)
 * Comment: I agree that the current location in Wikibooks is not ideal. The plan is to move the material into the into the far more active Linear algebra Wikibook, which is a featured book and actively used in university courses. However, because the linear algebra book is featured and quite visible, I am still waiting for some criticism/opposition on the Wikibooks:Linear algebra talk page before doing so.
 * I think the Moore-Penrose inverse would be a great addition to the linear algebra wikibook, since even though it is not usually covered in undergraduate linear algebra courses, it is useful, accessible and very pretty. Felix QW (talk) 08:20, 10 February 2022 (UTC)
 * Comment: @Felix QW I agree that Linear algebra looks like a better place than Topics in Abstract Algebra. I also agree that everything else being equal, Wikibooks would be a more appropriate place in general. But in practice, not everything else is equal. Looking at the page history of https://en.wikibooks.org/wiki/Linear_Algebra/Inverses, which would be a suitable sibling, there is significantly less editor activity there than on Wikipedia.
 * Thanks for your effort in rendering the content in textbook form. I like what you did there. Of course, those changes are appropriate only on Wikibooks, on Wikipedia the new phrasing would not be appropriate. It looks like you dewikified some or all wikilinks in the article. I do not see why. Was this necessary for some reason, could you please explain why you did not covert to Wikipedia links? One of the points of a wiki (even hypertext in general) is the use of links. --RainerBlome (talk) 00:18, 11 February 2022 (UTC)
 * Comment: The Removal of the links is explicit Wikibooks policy (I was also surprised) – in fact, when transwikiing a page from Wikipedia, it gets an explicit "dewikify" tag
 * wikibooks:template:dewikify! Felix QW (talk) 07:09, 11 February 2022 (UTC)
 * Rolling my eyes at that policy. Then the "Wiki" in "Wikibooks" does not fulfill expectations, for me. At least it doesn't say "no links", it just says "use sparingly". One more reason to keep the proof page at Wikipedia. :-)--RainerBlome (talk) 00:26, 12 February 2022 (UTC)


 * Delete, in support of the sensible plan to transwiki this to a better home. —David Eppstein (talk) 08:51, 10 February 2022 (UTC)

Remark: The page has around 850 page views per month. (https://pageviews.toolforge.org/?project=en.wikipedia.org&platform=all-access&agent=user&redirects=0&start=2015-07&end=2022-01&pages=Proofs_involving_the_Moore%E2%80%93Penrose_inverse) Were this much less, I might not bother to discuss here. The number of page views can be seen as a coarse indication of the current value of the page to the public, at its current location. This is our benchmark value. Would the value change? I do not know. For the sake of argument, let us *assume* that the value does not change much when the page is moved.

Seriously: What are the advantages, exactly, of moving the proof page? Rules such as WP:NOTTEXTBOOK have purposes. Actions should actually serve these purposes.

@XOR&#39;easter What does "more appropriate place" mean, appropriate in what way?

@David Eppstein What does "better home" mean, better in what way?

Answering "it would satsify the rule" isn't valid, the point of Wikipedia isn't to satisfy rules. What would be achieved by applying the rule?

Is Wikibooks a better place for the proofs? I have doubts.

We want to compare alternatives

[A] Keep in Wikipedia

[B] Move to Wikibooks

[C] Maintain a copy at both Wikibooks and Wikipedia

For the alternatives, let us imagine that we compare their effects at some point in the future, say ten years from now. Which alternative would yield a better Wikipedia? Which would yield a better world? Which would yield more value?

The point in removing something should be something like this:


 * We do not want to maintain this at Wikipedia. Doing so would worsen Wikipedia.


 * We do not want to host this at Wikipedia. Doing so would worsen Wikipedia.

As long as Wikibooks is stable (have all Wikimedia sites been stable so far?), I expect it to not really matter where the content is hosted, Wikibooks or Wikipedia. But I do expect it to matter where the content is maintained, at Wikibooks or Wikipedia.

--RainerBlome (talk) 00:26, 12 February 2022 (UTC) Please add new comments below this notice. Thanks, — Coffee  //  have a ☕️ //  beans  // 18:11, 13 February 2022 (UTC)
 *  Relisted to generate a more thorough discussion and clearer consensus.


 * Delete - the question discussed above is whether this is a wikibook article or a Wikipedia page. It clearly has the attributes of a wikibook rather than an article, as its approach is textbook-like, not encyclopedic. Chiswick Chap (talk) 18:37, 13 February 2022 (UTC)
 * Delete "Making the world worse" has nothing to do with Wikipedia notability guidelines, and this is not the place to WP:RIGHTGREATWRONGS. PianoDan (talk) 03:35, 16 February 2022 (UTC)


 * Keep - leaning here on a personal bias lol, but I just wanted to look something up related to this topic and found the answer reasonably quickly on this specific page, which if nothing else meets the basic use case of an encyclopaedia. And another anecdote: I have never once stumbled across Wikibooks in the search for something. More importantly, there's nothing in WP:NOTTEXTBOOK specifically against proofs being in Wikipedia. Perhaps it could be argued that there are too many proofs, or they're too detailed, but that's an argument for trimming the page, not deletion altogether. At least some of this seems notable enough. 86.130.93.159 (talk) 04:46, 16 February 2022 (UTC)
 * Yes, there are too many of them, and yes, they are too detailed. I'd go further and say that none of them prove anything surprising; they mostly demonstrate that, yes, the operator works like a derivative should. Trim away all that ought to be trimmed, and there would be nothing left. XOR&#39;easter (talk) 02:23, 21 February 2022 (UTC)


 * The above discussion is preserved as an archive of the debate. Please do not modify it. Subsequent comments should be made on the appropriate discussion page (such as the article's talk page or in a deletion review). No further edits should be made to this page.