Talk:Main Page

We've gone social.
I've just setup a Twitter and FaceBook accounts for ProofWiki. If anyone is interesting in helping out with the facebook page let me know. --Joe (talk) 15:40, 4 October 2012 (UTC)


 * We've already had a comment on Twitter appreciating our Template:Handwaving ... Sheer class. --prime mover (talk) 16:53, 4 October 2012 (UTC)


 * Should anyone find or post locate something worthy to share with the world, don't hesitate to request a tweet. I for one have just posted about Group Example: inv x = 1 - x. --Lord_Farin (talk) 21:04, 10 October 2012 (UTC)

Spam

 * Changed to use reCAPTCHA. Hopefully this will solve some spam issues. --Joe (talk) 11:14, 10 October 2012 (UTC)


 * ... and instantly a spam posting appears.
 * Interestingly the precise same message from the precise same username (Jeremykippler728) has just been deleted by me from another website I assist in moderating. That website has a horrifically bad problem with spammers, and (mow I think about it) may be a major contributor towards my chronically bad temper. --prime mover (talk) 20:13, 11 October 2012 (UTC)

I'm not sure what else to be doing to stop the spam. --Joe (talk) 20:15, 11 October 2012 (UTC)


 * Can you go back to what we had before yesterday? It was considerably more effective than reCAPTCHA which is showing the same weaknesses as I'm having serious problems battling elsewhere. --prime mover (talk) 22:30, 11 October 2012 (UTC)

I think I've mitigated the spam problem for the time being. Changing the question we were asking seems to have done the trick. It's not a question anymore, just a copy the following "blah...." into the provided box. --Joe (talk) 01:37, 22 October 2012 (UTC)

Xymatrix
Allow me to draw your attention to this fantastic package again. Through the hard work of sonoisa, the xymatrix commutative diagram drawing package is now implemented.

A few months ago, the more powerful (but also more difficult and cumbersome) back-end language for xymatrix, xypic, was introduced, which I have employed several times.

But now, with xymatrix, I feel that most PW users should be able to draw the CDs they need. Documentation for xymatrix is easily located through a web search, but I find http://www.jmilne.org/not/Mxymatrix.pdf to be a good source.

The package can be used inside a xy environment, like so:

$\begin{xy}\xymatrix{

//xymatrix code here

}\end{xy}$

I have adopted the convention to precede such diagrams with two colons :: so as to place it a bit more centered in the flow of text.

In case you find functionality of xymatrix that is not yet supported by the implementation, notify me; I'll pass it through to sonoisa. That's all for now - happy editing. --Lord_Farin (talk) 19:52, 20 October 2012 (UTC)


 * I'm currently not in the area of mathematics which requires me to use this - but I will give it a workout once I need to. What I see of its results looks good. --prime mover (talk) 05:23, 22 October 2012 (UTC)


 * Should the basic reference above be insufficient for your purposes, then check out this, or as a last resort (very technical but complete) this. --Lord_Farin (talk) 17:35, 22 October 2012 (UTC)


 * I am still sorting these issues out for myself, but does this mean, in particular, that you implemented commutative diagram capabilities by installing XyJax</tt> 'extension' of MathJax</tt>. Or, instead, are you running xymatrix</tt> as a math system separate and apart from MathJax</tt>, such that the latter is used to do most math typography, but for commutative diagrams, a separate system is used ? Thanks and regards --Pickle (talk) 04:09, 7 January 2013 (UTC)


 * We have the XyJax extension installed - it supports the \xymatrix</tt> command now. How to implement the extension is explained at its web site. --Lord_Farin (talk) 08:42, 7 January 2013 (UTC)


 * Noted and many thanks. --Pickle (talk) 13:02, 7 January 2013 (UTC)

Equation template amendment
I have amended the eqn template to put the "ro" column to the left of the "r" column so as to be able to build multi-line expressions on the right with greater effectiveness. See this in effect on the $> 1$ proof in Minkowski's Inequality for Sums (incidentally up for a major refactor). --prime mover (talk) 11:23, 4 November 2012 (UTC)

Axiom namespace
It occurs to me that Definition:Group Axioms, Definition:Open Set Axioms and also potentially the axioms for a Definition:Synthetic Basis should perhaps all be somewhere in the Category:Axioms namespace.

Of course, that will mean the Sysyphean task of changing Definition:Group Axioms to Axiom:Group Axioms and all the appropriate pages (and also for Open Set Axioms but there are little links for that yet).

Anyone else think that's a good idea? Oh please say no, my fingers hurt. --prime mover (talk) 22:38, 5 November 2012 (UTC)


 * I'd say no. Almost every concept defined introduces its "axioms". You have probably noticed yourself referring to them as "conditions" as well. I can't craft a definitive argument, though. It seems so natural to have Peano's axioms in the Axiom namespace. It also feels natural (to me) to not include the "totally ordered field axioms" there. Maybe the benchmark is that a certain axiom system should be more-or-less universal, or at least universally accepted as a possible axiomatisation (like e.g. Hilbert style deduction axioms for PropLog). Abstract algebra and topology seem to be less suitable for such axiom systems. --Lord_Farin (talk) 22:55, 5 November 2012 (UTC)


 * As is apparent from my answer, there is a case for this change. However, I think that we're better off tidying proofs, refactoring pages and eviscerating stubs than letting our fingers bleed for such an ultimately aesthetic change. --Lord_Farin (talk) 22:58, 5 November 2012 (UTC)


 * I have an idea PM if you're quite serious about your fingers hurting. Perhaps make something that could take "[ [D:Set union] ]" and turn it into "[ [Definition:Set Union] ]" (that could of course be extremely difficult I don't know).
 * I am quite confused as to what an axiom is in any given context due to conflicting sources. Some sources call proof rules axioms, others make no distinction between an axiom and an axiom schema and others further still call the defining properties of a class the axioms of some theory about that class. I understand all these senses and that the essential quality they have in common is that they are starting points but I wish there was a bijection between words and concepts. I will have to leave it up to you. --Jshflynn (talk) 01:29, 6 November 2012 (UTC)


 * No I'm sorry, you've lost me again: why would I need to turn [ [D:Set union] ] into [ [Definition:Set Union] ]? It already does say [ [Definition:Set Union] ] thruout. --prime mover (talk) 06:16, 6 November 2012 (UTC)


 * As far as I'm aware when creating an article you have to type [ [Definition:Something] ] over and over when you want to refer to a definition page. It might be easier if upon saving a page some program could turn [ [D:Something] ] into [ [Definition:Something] ] (you know like \R instead of \mathbb{R}). The idea being that it would do the transformation once you press the save page button (so people in the future would still see it as [ [Definition:Something] ]). It is just an idea though and may save no time at all to someone such as yourself. --Jshflynn (talk) 09:46, 6 November 2012 (UTC)


 * Interesting that you say that. I suspect it not to be too hard to implement this; I'll discuss it with Joe. In fact, MediaWiki already supports a similar feature, which I happily use: if you type, say  Definition:Set Union </tt>, that becomes Set Union. Make use of it :). --Lord_Farin (talk) 13:12, 6 November 2012 (UTC)


 * On the note of making shortcuts, if it is simple to implement them, can we make one for \operatorname? --GFauxPas (talk) 14:26, 6 November 2012 (UTC)


 * I see that the shortcut LF mentioned works for other namespaces too (even nonexistent ones should you need to implement them in future). How delightfully efficient :)

Changing letters
I have recently seen that some editors prefer the use of the symbols $S$ or $A$ rather than $X$ to denote topological spaces and the like, because "$X$ tends to denote an unknown." I have no objection against this, but I cannot comprehend why this is an improvement. Would anyone mind to explain this (somewhat) more thoroughly? --abcxyz (talk) 00:06, 18 November 2012 (UTC)


 * Whim. --prime mover (talk) 08:45, 18 November 2012 (UTC)


 * It's good to have consistency of presentation in a wiki. When the topology work was started, a lot of the original work had $X$, a lot had $A$ and a lot had $S$, depending on who posted up what. Either we leave it like it is, with lots of different symbology, or we make an attempt to bring it into line. I've been working hard on generally trying to bring consistency to the site, and it cna be frustrating to find that what I'm doing has been undone. --prime mover (talk) 09:13, 18 November 2012 (UTC)


 * Fair enough. I haven't bothered to go through all the topology pages and see which symbols are more common than others.
 * Also, I have a question about linking to redirects (such as  Definition:Neighborhood of Point </tt> as opposed to  Definition:Neighborhood (Analysis)/Topology/Point </tt>). Would anyone mind to explain why this is done? I just don't understand it. --abcxyz (talk) 19:13, 20 November 2012 (UTC)


 * It is mainly for two reasons:


 * 1) Prettier text when hovering over a link
 * 2) In the case a page gets refactored in the future, only the redirect needs to be adapted; this saves mountains of work


 * I'm sure you understand now. As far as I'm concerned, the second argument is the more important of the two. --Lord_Farin (talk) 19:38, 20 November 2012 (UTC)


 * Thanks; I hadn't thought of that. It appears to be a good idea. --abcxyz (talk) 21:10, 20 November 2012 (UTC)

clock
Any chance of getting the system clock reset? It's 5 minutes or more fast. --prime mover (talk) 23:05, 19 November 2012 (UTC)
 * I shall see what I can do! --Joe (talk) 22:23, 20 November 2012 (UTC)
 * Fixed. --Joe (talk) 13:25, 21 November 2012 (UTC)
 * Much better. I no longer panic when I see the time on a page I've just edited. Thx. --prime mover (talk) 08:29, 22 November 2012 (UTC)

Of vs. for (moved from Talk:Equivalent Definitions of Direct Limit of Sequence of Groups)
We now have Equivalent Definitions for T5 Space and this page [ Equivalent Definitions of Direct Limit of Sequence of Groups, LF]. There are various other names for this kind of page (e.g. "Equivalence of Definitions of ..."). We need a consistent convention. What will it be? I like "Equivalent Definitions" better than "Equivalence of Definitions" (it's shorter). --Lord_Farin (talk) 18:22, 26 November 2012 (UTC)
 * Pedantically, "Equivalence of Definitions ..." is more accurate, as "Equivalent Definitions ..." suggests that the definitions themselves are being introduced on that page - whereas the definitions themselves are in fact elsewhere. I confess I have not thought it through; but were we to use the latter it ought to be "Equivalent Definitions of ..." not "... for ..." (when I was refactoring over the weekend, "for" felt wrong) but I'm not in the mood to change them all at the moment.


 * If someone else were to volunteer to do the work, then making everything either "Equivalence of Definitions of..." or "Equivalent Definitions of..." would work for me. --prime mover (talk) 18:50, 26 November 2012 (UTC)


 * The new structure with definitions on subpages makes it much easier to have these pages adhere to a common standard, and to ensure that updates on the def. pages get reflected properly on other pages. --Lord_Farin (talk) 13:55, 27 November 2012 (UTC)

What to do about bad work
Some of the work on this site is shockingly bad. This has got to stop.

I recommend that people who post up unacceptable pages get punished for it. I recommend a fine of up to and including 1000USD and a ban from posting for up to and including life.

That's the only way we can get the quality of submissions up to a decent level. --prime mover (talk) 07:09, 27 November 2012 (UTC)


 * I don't deem it commendable to expel new enthusiasts adding a proof for a previously stubbed article because their writing style is not as we demand it. I do however agree that users notorious for posting substandard material (not that I know many) should be warned and if necessary restricted to their own user page until they demonstrate to know how to make stylistically bearable contributions. I fear that a too repressive regime (and I'd say we're already pretty relentless, only not finding the time to display it) would scare off (highly desired) new contributors, thus limiting the influx of information unnecessarily. --Lord_Farin (talk) 13:55, 27 November 2012 (UTC)


 * Bad formatting and lack of attention to appropriate writing style is not a problem. It's bad mathematics that I was suggesting needs to be eliminated. --prime mover (talk) 19:41, 27 November 2012 (UTC)


 * Would you care to give a rather more objective description of what you consider 'bad'? Plainly false, or incoherent, or phrased in specialists' language? --Lord_Farin (talk) 19:47, 27 November 2012 (UTC)


 * In particular, invalid arguments like affirming the consequent. Incoherent as well. Specialists' language is fine, it just needs someone to come in and say "This means ..." and so on. --prime mover (talk) 20:17, 27 November 2012 (UTC)

Repeating the hypotheses
When I was at school and my perspiring perpetually-defeated teachers tried vainly to bludgeon the basics of mathematics into the solid lump of bone that passes for my skull, one of the rules actually caught hold. That one is: when you're answering a question, it makes sense to repeat the basic facts of the question at the top of your answer so you have a precise grasp of your hypotheses.

In this context, I believe it does no harm to repeat the hypotheses of the theorem within the body of the proof (at the top) in order to clarify the statements which hold at any particular time.

It does no harm to repeat the hypotheses in the proof. OTOH, I think it would be bad to insist that "All hypotheses need to be repeated at the beginning of all proofs and all new work is to be abandoned until every proof adheres to this commandment". But there's a case for saying: if a hypothesis has been repeated at the top of a proof, it does not necessarily improve the proof by removing it just because you can. --prime mover (talk) 19:48, 1 December 2012 (UTC)


 * Fair enough. I'll take this bullet. --Lord_Farin (talk) 20:10, 1 December 2012 (UTC)


 * OK, fair enough. I removed the phrase to make the proof easier to read; it was at the end of a rather lengthy sentence. (Not that you said I "removed it just because I could", but this is why.) Moving it to the beginning of the proof also does the job. --abcxyz (talk) 21:57, 1 December 2012 (UTC)


 * Same thing happened somewhere else I think, I misremember exactly where. No worries. --prime mover (talk) 22:30, 1 December 2012 (UTC)

Differentiation and integration
Is there already a proof that the derivative of the integral of $f$ is $f$, i.e., that differentiation and integration are inverses? — Timwi (talk) 12:29, 3 December 2012 (UTC)


 * Cf. Fundamental Theorem of Calculus (first part, I think). --Lord_Farin (talk) 12:31, 3 December 2012 (UTC)

On results for concepts that have multiple definitions
We have recently decided to try and treat all (sourced) definitions for a concept on equal footing. An example of how the site is progressing can be found at Definition:Connected (Topology)/Topological Space. In time, Definition:Exponential will go through a similar remodeling, and I hope to add other descriptions of a Definition:Boolean Algebra. This brings me to the following point, concerning how results on such "multi-defined" concepts should be structured. As it stands, we have pages like Exponential as Limit of Sequence; this will of course become irrelevant given that we may define the exponential in terms of this limit. Such pages therefore naturally move to the associated Equivalence of Definitions result.

Up to now, such has not posed a problem. However, in the case of Boolean algebras, we have results of the kind Meet is Commutative, or, more relevantly, Join Distributes over Meet. In order to prove that a BA may equivalently be defined as a complemented, bounded, distributive lattice, it is then required to effectively prove Join Distributes over Meet to establish the equivalence. OTOH, given that a BA is a distributive lattice, the result is not even a result, but plainly imposed. Because there are rather a lot of such results involved in proving equivalence of the definitions, there are two, both unappealing paths that I see:


 * Firstly, that the pages remain in place, and have a "this is by definition" one-line proof (which seems rather irrelevant).
 * Secondly, that the pages become lemmata on the Equivalence of Definitions page, thereby unnecessarily lengthening that page (and I can foresee it will already be quite comprehensive from itself).

Of these options, neither of which is satisfying my elegance standard, I'd prefer the first, if one were to be chosen. We are also approaching a similar issue with the natural numbers. There are a lot of results which either prove basic facts about certain paradigms, or prove partial equivalence of definitions, or prove things by means of one paradigm that are trivial in another (without mentioning the equivalence).

It will benefit the consistency and completeness of ProofWiki if we pursue a meta-structural approach that treats, to the extent possible, definitions on an equal footing. In the long run, this will:


 * Make proving stuff easier, because the paradigm(s) most suitable to a typical can be invoked to achieve results that are nearly infeasible to prove directly from other definitions.
 * Make ProofWiki more appealing to all mathematicians, since there is no need for abandoning preferred frameworks and mindsets.
 * Make the site easier to navigate, and make it easier to locate what one is looking for; to this end, the "Also known as" sections should be as comprehensive as possible.

While I am convinced (as is apparent) that this is the situation ProofWiki should pursue, I think it is of the utmost importance that all editors are aware of, and should be able to comment on, this new direction, before we start rolling back each other's edits and create a hostile environment where the covering of mathematical knowledge is no longer the paramount goal of every editor. Thus, please comment. --Lord_Farin (talk) 14:10, 4 December 2012 (UTC)


 * Completely agree.


 * There are two types of definiend here:


 * One, e.g. Connectedness, which is one particular concept which can be treated monolithically; equivalence is proved "in one step", so to speak.


 * The other type of definiend exemplified is that of natural numbers, which is defined by means of an axiom schema - and in this case there are several approaches. In this case, what is done is for separate threads to be established, each one aiming towards the "defining properties" of the natural numbers - and indeed, some of the proofs along the way may be trivial.


 * The transition from the definition-and-equivalences to the multiple-definitions paradigm can be fraught with trouble if other editors are simultaneously trying to "correct" stuff which is still in the process of being developed, but if we are rigorous about using (and respecting) templates indicating work in progress / refactoring / etc., and perhaps adding a field for a username to those templates which do not have them, then inter-editor friction should be kept to a minimum.


 * I would also exhort newer editors to learn the ropes before being too strident in their opinions of how they think things ought to be. Many of the structural conventions have evolved over time and (despite appearance to the contrary) do actually make sense. Some MediaWiki tools and MathJax constructs, for example, are specifically not utilised because they have been shown to cause problems (although with more recent releases of the s/w some of these may well have been resolved).


 * In short, if new editors find their work is being systematically altered, tagged, refactored etc. etc. then treat it as a learning experience as to how pages are to be styled rather than as a challenge to their creative abilities. They are invited to take note of the changes being made and adjust their style accordingly. There are reasons. --prime mover (talk) 15:03, 4 December 2012 (UTC)


 * As to that last point of PM, I'd like to stress that anyone who doesn't understand a certain edit is urged to ask the relevant editor for a justification. In this way, we are both ensured that people get the rationale behind paradigms such as house style, and that such rationale continues to exist in the first place. All editors are invited to put up examples of possible changes/advances in house style or otherwise on their user sandbox, and invite others to comment. This seems to me like the appropriate way to try and nudge the rules and regulations for editing in one's preferred direction (as opposed to simply posting pages in the newly desired format in the main wiki). --Lord_Farin (talk) 22:13, 4 December 2012 (UTC)


 * Sounds good. I have a question about proofs (e.g. Synthetic Sub-Basis and Analytic Sub-Basis are Compatible) that use multiple definitions of a concept (in that case, the generated topology). Evidently the equivalence proof has to be mentioned somewhere. I can't think of a way to deal effectively with pages such as those. Any ideas or comments?


 * Less importantly, does anyone find the phrase "the definition" strange, when one of the multiple definitions is being invoked? --abcxyz (talk) 16:52, 16 December 2012 (UTC)


 * Obviously what's happened is that the proof was written before the refactoring was done on the definition page to split it into multiple definitions. Equally obviously, the proof needs to be rewritten accordingly. --prime mover (talk) 18:22, 16 December 2012 (UTC)


 * Both definitions were still invoked (before the refactoring), so I don't see how the refactoring matters. (This was always a problem; I just didn't bring it up until now.) --abcxyz (talk) 18:37, 16 December 2012 (UTC)


 * So I haven't got round to sorting it out yet. My fault. I will try to do better. I understand my employment is up for review. Please feel free to vote on whether I get to continue to be allowed to contribute. --prime mover (talk) 21:33, 16 December 2012 (UTC)


 * No, it's not your fault one bit. I posted the proof and I want to know if anybody has an idea about how to make it work better. --abcxyz (talk) 21:38, 16 December 2012 (UTC)


 * Link to the specific subpage holding the definition you need in order to provide the required property that will move your proof along? --prime mover (talk) 21:54, 16 December 2012 (UTC)


 * Sorry, what required property? --abcxyz (talk) 23:35, 16 December 2012 (UTC)


 * Whatever property of whatever object you are using whatever definition of to prove whatever theorem you're writing a proof of. --prime mover (talk) 06:51, 17 December 2012 (UTC)


 * If I'm understanding you correctly, I think I did that already. The problem is that both definitions are used in the proof. --abcxyz (talk) 04:23, 18 December 2012 (UTC)


 * So link to one definition at the point at which you use that definition, and link to the other definition at the point at which you use that one. --prime mover (talk) 01:04, 26 December 2012 (UTC)


 * That's exactly what I did. So that's enough because the equivalence proof is in the "Also see" section of the definition page? --abcxyz (talk) 16:37, 8 January 2013 (UTC)

Enough for me, at least if you refer to "Definition X of ...". --Lord_Farin (talk) 17:53, 8 January 2013 (UTC)


 * Like this? --abcxyz (talk) 18:00, 8 January 2013 (UTC)


 * Yes, that's what I meant. In this way, it is apparent to the reader that there are multiple definitions, which may be overlooked otherwise. --Lord_Farin (talk) 18:02, 8 January 2013 (UTC)

Sine and Cosine of Sum
I split this (and all its subpages) into Sine of Sum and Cosine of Sum. Please let me know how I did! — Timwi (talk) 15:00, 13 December 2012 (UTC)

What should we do with the page Sine and Cosine of Sum now? Delete? Redirect to one of the two (which is what it does now)? Turn into a disambiguation page? The latter two seem silly, but the first one breaks existing links. — Timwi (talk) 15:00, 13 December 2012 (UTC)


 * From what I see, it looks good. Tasks still to be done are to make all links to Sine and Cosine of Sum point to the appropriate page and to turn Sine and Cosine of Sum into a transclusion amalgamate of Sine of Sum and Cosine of Sum. --Lord_Farin (talk) 15:19, 13 December 2012 (UTC)


 * Is that really necessary?... — Timwi (talk) 15:31, 13 December 2012 (UTC)


 * Such pages form convenient entry points to PW for wandering people doing web searches. While they are not strictly speaking necessary, they serve largely to disclose PW to incoming traffic. --Lord_Farin (talk) 15:33, 13 December 2012 (UTC)


 * OK well, I did the “simple” thing of just transcluding the two (see Sine and Cosine of Sum now), but it means it doesn’t have the proofs, and getting to the proofs is unobvious (you have to know that clicking the link in the header takes you to a proof...) — Timwi (talk) 17:38, 13 December 2012 (UTC)


 * If there's an existing page split into several, it is never a good idea to delete such a page. As you say, it breaks links. And even once the internal links are all amended, there may be external links which access this site from all over the place which would suddenly arbitrarily fail, particularly for old pages. It is also usually a bad idea to leave it as a redirect, because e.g. "blah blah sine and cosine blah" suddenly going to page containing "blah blah sine blah" etc., the reader is going to justifiably feel annoyed at not finding the cosine there. This contributes towards the generally negative view in which this site is held in the great wide world outside. --prime mover (talk) 17:41, 13 December 2012 (UTC)


 * We'll have to find a way to make clear that clicking links will take people to proofs, either now or some time in the future. As it stands, several people (rightfully IMHO) have indicated that the system isn't self-explanatory for non-veterans. Ideas are most welcome. --Lord_Farin (talk) 17:45, 13 December 2012 (UTC)

Separation of Proof and Theorem pages
Take for example Arctangent Logarithmic Formulation.

How necessary is it to put the proof on a separate page from the statement?

My idea was that we put the theorem and proof on the same page, except where we have multiple proofs in which case we separate out the proofs into different pages.

Have I been doing it wrong all this time? --prime mover (talk) 07:00, 14 December 2012 (UTC)


 * To the best of my knowledge, no. No need for duplication unless it allows for proper referral to knowledge. Your current approach to refactoring is reasonable and should be retained. --Lord_Farin (talk) 11:44, 14 December 2012 (UTC)

Template:Refactor
Personally, I’m quite confused by the fact that you seem to use the same template for two completely different meanings: I think we should split this into two to distinguish these two meanings. — Timwi (talk) 11:51, 15 December 2012 (UTC)
 * “Someone is currently working on this page, please don’t edit it”, and
 * “A change to this page is desirable, please edit it”.

And for the please edit it one, I think the template should mandate that whoever put the tag on the page should explain what it is that needs refactoring, otherwise the tag is not useful. — Timwi (talk) 11:51, 15 December 2012 (UTC)


 * My personal view is that until a person has a good overall feel for the structure behind the website, it would be preferable for that person to concentrate on adding new stuff rather than tidying up the existing structure. --prime mover (talk) 21:33, 15 December 2012 (UTC)


 * And how might one get such a “good overall feel”? By jumping in and doing it, not by staying away. — Timwi (talk) 22:37, 16 December 2012 (UTC)


 * The refactor template is to the best of my knowledge not used in the first sense. Template:Inuse is the thing supposed to do that, but it seems to have fallen into obscurity. As to the explanation: sometimes the work required is either blatantly obvious to its intended audience (site maintenance workers) or hasn't fully crystallised yet (in which case it functions like a stronger version of Template:Improve). Since until very recently, I and PM were the only ones in the "maintenance workers" group (he more so than I) there wasn't really a need. I'll try to explain things better in the future. --Lord_Farin (talk) 21:39, 15 December 2012 (UTC)


 * Perfect — in that case, I’ll be bold and remove the first sentence from the template. If you disagree, feel free to revert it and then perhaps we should move this discussion to Template talk:Refactor. — Timwi (talk) 22:37, 16 December 2012 (UTC)


 * Reverted it, and protected so that only editors with admin privileges can edit it. Sorry, but it was correct as it is: it has either been identified as a candidate for refactoring, or it is in the process of being refactored. That is how it is being used.


 * The bottom line is: if there is a maintenance template whose purpose you do not fully understand, then it would be better to leave it alone. Basically, such a tag was not meant as an invitation to all to contribute, but more as a flag to a particular few who have been involved in what is an ongoing major restructure of the fundamental architecture on which ProofWiki is based.


 * TL;DR: thanks for the offer but we have the refactoring under control because we know precisely where we are going with it. Please work on other stuff. --prime mover (talk) 22:55, 16 December 2012 (UTC)

FAQs
The same questions (perfectly legitimate and sensible) are being asked by different contributors concerning things like house style, philosophical approach, structural conventions and all sorts of non-obvious and seemingly arbitrary stuff which we impose on the entries on this site.

It might be a good idea to bag up some of these, e.g. "Do we really need to put \left and \right round every parenthesis and if so why?" and "Why did you delete my link to Wikipedia in the citations?" and "Why did you change my favourite notation?" and publish them on a FAQ page - so if they get asked again, we can point the asker to that page.

Thoughts? --prime mover (talk) 00:11, 16 December 2012 (UTC)


 * I think this is a good idea! --Joe (talk) 12:31, 16 December 2012 (UTC)


 * Okay - I don't feel like working on it immediately, but as and when questions crop up that have been asked before, I will probably start building such a page. --prime mover (talk) 13:19, 16 December 2012 (UTC)


 * I don't know why we didn't have this page earlier! --Joe (talk) 15:02, 20 December 2012 (UTC)


 * May I recommend implementing a system to uniquely identify the questions? This will lend itself to redirecting inquiries. --Jshflynn (talk) 18:36, 20 December 2012 (UTC)

Something wrong with the rendering of references
Does anyone know why we’re getting the rendering bug shown in the screenshot on the right? I looked at the page source, it looks fine, so the bug must be with the parser or the template system... — Timwi (talk) 14:05, 20 December 2012 (UTC)


 * It's the parser, I think. Something is wrong with how it handles nowiki tags (e.g. around square brackets for references). Various talk pages are littered with my remarks on the matter. --Lord_Farin (talk) 14:27, 20 December 2012 (UTC)


 * Once the templates have been cleared it should render okay. Anyway, house style discourages footnotes. --prime mover (talk) 17:32, 20 December 2012 (UTC)


 * ... oops: I notice that that was a page I wrote myself. Definitely needs a rethink ... I was infodumping a college course. --prime mover (talk) 18:19, 20 December 2012 (UTC)

Milestone approaching
We are 36 proofs away from the 7000th proof.

As this is a small number times a higher power of 10 (in this case a cube), this number would appear to have significance to a hypothetical race of intelligent beings which have a 10-based number system (probably because they have ten fingers or something silly and arbitrary like that).

On this website it is traditional to reserve such a number to be the ordinal of a particularly significant result. I therefore alert all active contributors to this site to keep an eye open for something significant which can be hooked onto this number, and make sure it is not something simple and/or trivial.

Newcomers: take a look in the "Landmark Pages" category for an idea of what (at least in recent times) sort of thing I mean. Note that at this stage it is not necessary to have a proof immediately available if you need some space to work up to it. --prime mover (talk) 23:03, 24 December 2012 (UTC)


 * My suggestion is Law of Large Numbers. It's the first significant result of probability calculus, and we don't have it yet. If we restrict ourselves to the Weak Law of Large Numbers, it should also be possible to prove the Lemmas that are required to prove the theorem. If you find that LLN is too trivial, then I'd suggest the Central Limit Theorem. --Anghel (talk) 18:44, 25 December 2012 (UTC)


 * If you happen to be sitting in front of your screen when proof 6999 appears, then you are more than welcome to post up LLN as the 7000th, or, if you prefer, CLT. :-) --prime mover (talk) 01:02, 26 December 2012 (UTC)


 * CLT was already up. I put up something quirky, although nowhere near being able to put a proof up at the moment. --prime mover (talk) 21:26, 31 December 2012 (UTC)

Duality
I have been thinking about a way to connect dual pairs of theorems like Infimum of Infima and Supremum of Suprema. What I've come up with most recently is something like Template:About, i.e. a sentence below the theorem title. It could be along the following lines:
 * The dual of this [theorem/definition] is Infimum of Infima. See Duality Theorem (Ordered Sets) for more information on duality.

where of course there are three parts ("[theorem/definition]" and the two links) that need to be changeable by the template governing this. Possibly we want to say "information on duality for [concept duality applies to]". Maybe the last two links may be governed by a standard setting like  or s.t. along those lines. Thoughts? --Lord_Farin (talk) 18:23, 3 January 2013 (UTC)


 * a) How well-defined a concept is "duality" apart from it being an intuitive thing?


 * It can be made quite formal, by e.g. interpreting a definition in the Definition:Opposite Ordered Set (defined along Inverse of Ordering is Ordering), and then translating that statement back to the original poset. This process is described in more generality on Duality Principle (Category Theory) (although stated there for theorems, it can easily be extended to cover definitions as well).


 * b) I'm not happy about it being right at the top of the page - too much of that and the statement becomes in danger of getting "lost" so to speak. In the "Also see" section sounds more appropriate, where most of these duals already exist - suppose it does no harm to emphasise their duality. --prime mover (talk) 19:40, 3 January 2013 (UTC)


 * Meh. The Also see section is an option, but I feel this detracts from the importance of duality. OTOH, a dedicated section titled "Dual something" could easily turn into overkill. If there were a nice option to stylistically emphasize the dual theorem, along with a few accompanying words, that'd be great. Maybe we have to settle with the dedicated section nonetheless. --Lord_Farin (talk) 20:46, 3 January 2013 (UTC)


 * So, I've decided to delve into the task of covering duality (for ordered sets only at this point). Would we like to anticipate on similarities coming up in the (hopefully not too distant future) concerning duality for ordered sets, groups, lattices, boolean algebras, categories (incidentally the last covers all the others) and call everything "Dual Blabla", i.e. "Dual Ordered Set", "Dual Ordering" (currently Definition:Opposite Ordering), "Dual Group" (Definition:Opposite Group), "Dual Boolean Algebra". Definition:Dual Category is already up. I have a feeling that this path will contribute to a more cohesive feeling for the whole site. --Lord_Farin (talk) 19:02, 4 January 2013 (UTC)


 * Can I just leave it up to you to see what it looks like? Maybe when I see it in action I'll like the look of it ... you know me, anti any idea that gets floated in a talk page, but once I see it working I usually quite like it. --prime mover (talk) 21:07, 4 January 2013 (UTC)

Question regarding use of copyrighted sources
I was wondering about sourcing proofs from copyrighted works, and what is permissible. Are there any guidelines on this from a legal perspective? To what extent can a proof be copyrighted? If a proof can not be copied in verbatim, to what extent must it differ from the original to avoid infringement?

--Icarus (talk) 16:10, 5 January 2013 (UTC)


 * I'm afraid it's hard to put a definitive line in the inevitable greyscale area between "copied verbatim" and "rewritten in own words". However, if it's not self-evident that there are no legal issues, you're probably pushing it. That should be a safe guideline to work with. --Lord_Farin (talk) 20:12, 5 January 2013 (UTC)

Oddness in Chrome
On my machine, when you try to edit a page in Google Chrome, it changes from (Courier New) font to some other font (some naff san-serif font that's all tiny and narrow and not equal-width, making it difficult to edit). It does this in all applications, not just ProofWiki. Even does it on Facebook.

Anyone experienced this? Only just started doing it. Version 23.0.1271.97 m.

I've sent a feedback note to Google in case it's something their end. Any advice? I lack the patience to dig around in the source code to debug it myself. --prime mover (talk) 20:02, 5 January 2013 (UTC)


 * I use the exact same version of Chrome, and I still get Courier New. --Lord_Farin (talk) 20:08, 5 January 2013 (UTC)
 * I think a solution is to add the code:

textarea{ font-family: monospace; }
 * to your user.css. This will force the textarea HTML environments (like the edit window is) to use a monospace font. --Lord_Farin (talk) 20:08, 5 January 2013 (UTC)


 * Doesn't work. As I say, it's not a ProofWiki issue, it does it all over, on all websites.--prime mover (talk) 20:20, 5 January 2013 (UTC)


 * Sorted it. In case anyone else has the same trouble, it turns out that I had Diigo bookmarked (it's an insidious little beast) which hijacks the stylesheet when in a textarea. Burn it with fire. --prime mover (talk) 22:44, 9 January 2013 (UTC)

Expressions involving restrictions
Just a quick note:

I noticed that the spacing of expressions involving restrictions can look somewhat awkward. For example:

is rendered as:
 * $f \restriction_A: A \to Y$

which doesn't look good. I think that a solution is to use braces, i.e.:

which is rendered as:
 * ${f \restriction_A}: A \to Y$

I have already done this in several places. --abcxyz (talk) 18:48, 8 January 2013 (UTC)


 * Well spotted. Maybe this technical note could be added to the Definition:Restriction page as well? --Lord_Farin (talk) 18:55, 8 January 2013 (UTC)


 * Sounds like a worthwhile structural paradigm: perhaps another standard section name below everything except "Also see" and "Sources" called "LaTeX technicalities" or some such. The exact wording of that subtitle may need to be discussed. --prime mover (talk) 19:07, 8 January 2013 (UTC)


 * Definition:Convergence in Measure uses "Technical Note" which we deemed to be pretty good back then. --Lord_Farin (talk) 19:10, 8 January 2013 (UTC)
 * I would say however that the section should be below Also see, because we don't want to burden the casual reader with LaTeX information they may well find obscure and irrelevant, aside of incomprehensible. --Lord_Farin (talk) 19:12, 8 January 2013 (UTC)


 * As we progress down the page we go to concepts less and less directly relevant to the item in question. As an "also see" is not directly about the subject, I would argue that the LaTeX for presenting the subject is more directly relevant, so therefore deserves to be above Also see.


 * Vote? --prime mover (talk) 19:43, 8 January 2013 (UTC)


 * The "Also See" section is about mathematics; the "Technical Note" is not. Thus, I would prefer having the "Also See" on top. --abcxyz (talk) 21:45, 8 January 2013 (UTC)


 * I completely agree with Abcxyz. The sources section is naturally at the bottom; this quite uniquely determines the position of the section. --Lord_Farin (talk) 21:51, 8 January 2013 (UTC)


 * Yep okay, no worries then. --prime mover (talk) 22:01, 8 January 2013 (UTC)


 * I'll just add this: the rendering of MathJax is different from how it renders in the MediaWiki LaTeX package, and so we had to go through and change a lot of the rendering. As MathJax evolves, presentational awkwardnesses are fixed and fiddly extras are no longer required. So it's possible that a recommended technical implementation on one version of MathJax may not be optimal on a later version (e.g. at the moment it is advisable to add a half-space before primes on certain letters, $T$ for example, otherwise the prime overwrites the letter making it obscured - it is possible that this may be fixed in future MathJax versions). So a technical recommendation for presentational optimality may change during the course of evolution of this site. --prime mover (talk) 22:07, 8 January 2013 (UTC)

I have added a "Technical Note" section to each of the subpages of Definition:Restriction.

I also noticed that, on this site, the restriction symbol (e.g. $\restriction_A$) is used as a unary operation on the relation/mapping. However, $\LaTeX$ apparently treats harpoons as binary relations, as it does for other arrows (e.g. $\rightarrow$). This causes an excessive (for my taste) space between the relation/mapping and restriction symbols. Thus, I suggest inserting braces around the restriction symbol instead, which results in:
 * $f {\restriction_A}: A \to Y$

In addition, this looks similar to $\preceq \restriction_A$.

Regarding the use of, its behavior seems to be the same as that of   (as in  , for example). That is, it treats its argument as a unary operation. When it is not intended as such, it can have an undesirable effect, e.g.:
 * $\operatorname{id}_X \mathop{\circ} \left({g \circ f}\right)$

which is produced by the $\LaTeX$ code:

One $\LaTeX$ command that treats its argument specifically as a binary operation is. I have used it in Definition:Restriction of Operation. It also can be applied to $\restriction$ as in $f \mathbin{\restriction} A$.

Correct me if I'm wrong on any of the above. Comments? --abcxyz (talk) 02:59, 10 January 2013 (UTC)


 * I'm (guardedly) in favour of replacing "mathop" with "mathbin" when the operator in question is binary, and using "mathop" instead for unary ones. As per current style, suggest the curly braces are used only when the operator itself is multipart, so e.g. you'd do  rather than  . This matches current usage of mathop and saves time when inserting new instances. --prime mover (talk) 06:13, 10 January 2013 (UTC)


 * Oh yeah, of course. Sorry, I just forgot. --abcxyz (talk) 16:51, 10 January 2013 (UTC)


 * Apparently the original suggestion to use "mathop" came from some $\TeX$ noob who encountered it on a quick web search. Braces around the harpoon seems a good idea because we want to treat it as a postfix operator. There is no dedicated $\TeX$ command for that, sadly. It may be that in certain rare cases the braces do not provide an adequate solution but the situations I can think of where this happens are very unlikely to be on PW, so we may decide to work with this (for the sake of brevity of source code). Thank you for your input on the matter, abcxyz. --Lord_Farin (talk) 09:03, 10 January 2013 (UTC)

Compare and contrast:
 * : $\displaystyle \sum_{i \mathop = 1}^n$
 * : $\displaystyle \sum_{i \mathbin = 1}^n$

On my setup  wins -- no contest. --prime mover (talk) 19:21, 10 January 2013 (UTC)

Parentheticals
The house style insists on $\left({blah}\right)$ in all cases rather than $(blah)$. There are three problems with this, ranked from most important to least important in my opinion:
 * It's much harder to read in source form, particularly when nested.
 * Try expanding the font size - that might help.


 * It takes longer to type.
 * Cut'n'paste works here.


 * It requires different structure for $\left\{{a} \,\middle|\, {b}\right\}$ than for $\left\{{a:b}\right\}$. --Dfeuer (talk) 22:15, 8 January 2013 (UTC)
 * The house style remains unchanged. --prime mover (talk) 22:22, 8 January 2013 (UTC)


 * Even if it takes longer to type, it's only by a couple of seconds (for me). As for your last point, I think  does the job. --abcxyz (talk) 22:24, 8 January 2013 (UTC)


 * does not automatically size:


 * $\left\{{\dfrac a b \mid \dfrac c d}\right\}$ (yes I know it's meaningless mathematics)


 * as against:


 * $\left\{{\dfrac a b} \,\middle|\, {\dfrac c d}\right\}$


 * One of the main reasons behind the rigorous enforcement of \left{ ... }\right is purely because of the resizing. Cut'n'paste on a given construct is more straightforward, you don't then have to put the left-right in. The irritation about adding the spaces either side of the \middle is a nuisance, I agree - but it's minor because that construct is not often used. --prime mover (talk) 22:34, 8 January 2013 (UTC)


 * Y'all do know of the mightily useful option of right-clicking a piece of rendered TeX, going to "Show Math As > TeX Commands" to obtain a small window with the TeX generating that construct, no? (Admittedly I only found out one minute ago, but that's not the point.) --Lord_Farin (talk) 22:37, 8 January 2013 (UTC)


 * Occasionally use it, but (a) muscle memory has developed facility typing \left etc., and (b) when I'm editing a page with a lot of f \left({x}\right) etc. cut'n'paste is easy. --prime mover (talk) 22:42, 8 January 2013 (UTC)


 * Muscle memory FTW :). --Lord_Farin (talk) 22:43, 8 January 2013 (UTC)


 * Let's not get hung up on my third point, which is relatively trivial. $\left({ \left({ f \left({x}\right) + g \left({y}\right) }\right) h \left({z}\right) }\right) ^ 2$ is just inherently harder to read in source form (and thus to keep track of while writing) than is $((f(x)+g(y))h(z))^2$, and they look the same once processed. As for cut and paste, unless you're really quick with your custom emacs/vi macros, that's going to be slow too. I understand the motivation to make cutting and pasting easier, but just how often does one replace a standard-height expression in parentheses with a tall one? --Dfeuer (talk) 22:45, 8 January 2013 (UTC)


 * Not so much less often than one needs more than two levels of nested bracing (in TeX, that is; regular contributors know I can get pretty deep in my prose (such as this illustrative yet meaningless phrase)), I would say. While I do admit the paradigm is awkward at first, it works quite well (says this one, having been fully internalised into PW). I'm still not inclined to change my view - sorry if that comes across as stubborn. --Lord_Farin (talk) 22:53, 8 January 2013 (UTC)


 * Let's suppose you're writing $((f(x)+g(y))h(z))^2$ and you make a mistake miscounting the brackets (easy to do). Using your preferred style:  you don't miss the missing close bracket in $((f(x)+g(y))h(z)^2$ but with this:   it doesn't render: $\left({ \left({ f \left({x}\right) + g \left({y}\right) }\right) h \left({z}\right) ^ 2$.
 * Case rests. --prime mover (talk) 23:05, 8 January 2013 (UTC)

I personally get confused/annoyed by quantified expressions, disjunctions, etc., that aren't sufficiently parenthesized, but these become relatively deeply nested once parenthesized enough, at which point I find them unreadable under PW style rules. Take, say $\forall x \in A:((3(x+a)<4) \lor (x>17))$. However: I would frankly be much, much happier if we even had a very slightly laxer rule, not requiring innermost parentheses to be fancified, while requiring it for all others. As for the automatic error detection, as you're clearly using a fancy editor with fancy custom macros I'm sure your editor is quite capable of checking for mismatched parentheses. --Dfeuer (talk) 23:19, 8 January 2013 (UTC)


 * I'm not using a fancy editor with fancy custom macros. Those are for girls. --prime mover (talk) 23:21, 8 January 2013 (UTC)


 * On-topic, I think there may be a case for Dfeuer's suggestion. It seemingly combines the best of the two approaches. I pose the slightly adapted suggestion that innermost parentheses with a content of just one entity (like e.g. $x$, $\overline \R$ or $\operatorname{id}_X$) needn't be endowed with lefts and rights. --Lord_Farin (talk) 23:25, 8 January 2013 (UTC)


 * I disagree because then somebody's going to go through all the existing pages and change them. I don't think that would be helpful. --prime mover (talk) 06:10, 9 January 2013 (UTC)