Property talk:P2534
Documentation
mathematical formula representing a theorem or law. Maximum length: 400 characters
Single best value: this property generally contains a single value. If there are several, one would have preferred rank (Help) Exceptions are possible as rare values may exist. List of this constraint violations: Database reports/Constraint violations/P2534#single best value, SPARQL, SPARQL (new) 
Conflicts with “instance of (P31): human (Q5), chemical compound (Q11173), concrete object (Q4406616), Wikimedia disambiguation page (Q4167410), Wikimedia human name disambiguation page (Q22808320)”: this property must not be used with the listed properties and values. (Help) List of this constraint violations: Database reports/Constraint violations/P2534#Conflicts with P31, hourly updated report, SPARQL, SPARQL (new)

Allowed entity types are Wikibase item (Q29934200): the property may only be used on a certain entity type (Help) Exceptions are possible as rare values may exist. List of this constraint violations: Database reports/Constraint violations/P2534#allowed entity types, SPARQL (new) 
Scope is as main value (Q54828448): the property must be used by specified way only (Help) Exceptions are possible as rare values may exist. List of this constraint violations: Database reports/Constraint violations/P2534#scope, SPARQL, SPARQL (new) 
limit 400 charactersEdit
Degen's eightsquare identity (> 400):
or LATEX (976 symbols): $ (a_{1}^{2}+a_{2}^{2}+a_{3}^{2}+a_{4}^{2}+a_{5}^{2}+a_{6}^{2}+a_{7}^{2}+a_{8}^{2})(b_{1}^{2}+b_{2}^{2}+b_{3}^{2}+b_{4}^{2}+b_{5}^{2}+b_{6}^{2}+b_{7}^{2}+b_{8}^{2})=\, $ $ (a_{1}b_{1}a_{2}b_{2}a_{3}b_{3}a_{4}b_{4}a_{5}b_{5}a_{6}b_{6}a_{7}b_{7}a_{8}b_{8})^{2}+\, $ $ (a_{1}b_{2}+a_{2}b_{1}+a_{3}b_{4}a_{4}b_{3}+a_{5}b_{6}a_{6}b_{5}a_{7}b_{8}+a_{8}b_{7})^{2}+\, $ $ (a_{1}b_{3}a_{2}b_{4}+a_{3}b_{1}+a_{4}b_{2}+a_{5}b_{7}+a_{6}b_{8}a_{7}b_{5}a_{8}b_{6})^{2}+\, $ $ (a_{1}b_{4}+a_{2}b_{3}a_{3}b_{2}+a_{4}b_{1}+a_{5}b_{8}a_{6}b_{7}+a_{7}b_{6}a_{8}b_{5})^{2}+\, $ $ (a_{1}b_{5}a_{2}b_{6}a_{3}b_{7}a_{4}b_{8}+a_{5}b_{1}+a_{6}b_{2}+a_{7}b_{3}+a_{8}b_{4})^{2}+\, $ $ (a_{1}b_{6}+a_{2}b_{5}a_{3}b_{8}+a_{4}b_{7}a_{5}b_{2}+a_{6}b_{1}a_{7}b_{4}+a_{8}b_{3})^{2}+\, $ $ (a_{1}b_{7}+a_{2}b_{8}+a_{3}b_{5}a_{4}b_{6}a_{5}b_{3}+a_{6}b_{4}+a_{7}b_{1}a_{8}b_{2})^{2}+\, $ $ (a_{1}b_{8}a_{2}b_{7}+a_{3}b_{6}+a_{4}b_{5}a_{5}b_{4}a_{6}b_{3}+a_{7}b_{2}+a_{8}b_{1})^{2}\, $ Fractaler (talk) 13:48, 8 September 2016 (UTC)
 This can be obviously compressed to 580 symbols:
$(a_1^2+a_2^2+a_3^2+a_4^2+a_5^2+a_6^2+a_7^2+a_8^2)(b_1^2+b_2^2+b_3^2+b_4^2+b_5^2+b_6^2+b_7^2+b_8^2)=(a_1b_1a_2b_2a_3b_3a_4b_4a_5b_5a_6b_6a_7b_7a_8b_8)^2+(a_1b_2+a_2b_1+a_3b_4a_4b_3+a_5b_6a_6b_5a_7b_8+a_8b_7)^2+(a_1b_3a_2b_4+a_3b_1+a_4b_2+a_5b_7+a_6b_8a_7b_5a_8b_6)^2+(a_1b_4+a_2b_3a_3b_2+a_4b_1+a_5b_8a_6b_7+a_7b_6a_8b_5)^2+(a_1b_5a_2b_6a_3b_7a_4b_8+a_5b_1+a_6b_2+a_7b_3+a_8b_4)^2+(a_1b_6+a_2b_5a_3b_8+a_4b_7a_5b_2+a_6b_1a_7b_4+a_8b_3)^2+(a_1b_7+a_2b_8+a_3b_5a_4b_6a_5b_3+a_6b_4+a_7b_1a_8b_2)^2+(a_1b_8a_2b_7+a_3b_6+a_4b_5a_5b_4a_6b_3+a_7b_2+a_8b_1)^2$ and by substituting each variable to one letter can be compressed down to 292 symbols: $(A^2+B^2+C^2+D^2+E^2+F^2+G^2+H^2)(a^2+b^2+c^2+d^2+e^2+f^2+g^2+h^2)=(AaBbCcDdEeFfGgHh)^2+(Ab+Ba+CdDc+EfFeGh+Hg)^2+(AcBd+Ca+Db+Eg+FhGeHf)^2+(Ad+BcCb+Da+EhFg+GfHe)^2+(AeBfCgDh+Ea+Fb+Gc+Hd)^2+(Af+BeCh+DgEb+FaGd+Hc)^2+(Ag+Bh+CeDfEc+Fd+GaHb)^2+(AhBg+Cf+DeEdFc+Gb+Ha)^2$ Infovarius (talk) 17:46, 10 September 2016 (UTC)
Symbol definitionsEdit
How to add symbol definitions? They were in the original propsal, where are they now? Ignatus (talk) 22:16, 10 December 2016 (UTC)
 Well, in the mass–energy equivalence (Q35875) I see the definirtions in has part (P527). But it is VERY bad semantically use of this property. Hardly the description should leave the formula's qualifiers since the letters define the formula, not the object (the symbols often vary in different traditions but the formulae built with them are equivalent if correctly defined). And we probably can't now make qualifiers with relation <math:symbol  item:definition> (and I'm afraid not any definition will have an item defining it, or we'll sink in items used to define formulae only, like in
Pithagor^{Heron, shame on my head}'s formula for area of a triangle ). Ignatus (talk) 22:30, 10 December 2016 (UTC) Opened a discussion on WD:Project chat/Archive/2016/12#Symbol definitions with math datatype 22:56, 10 December 2016 (UTC)  I would prefer using Datasets from Commons (mw:Help:Tabular data) as legends for formulae and images, they support structured lists, and even localization! Ignatus (talk) 20:11, 27 December 2016 (UTC)
Supported environmentEdit
I would like to insert the Butcher tableau of midpoint methods (Q17103851) as formula but I can't:
\begin{tabular}{cc c} 0 & 0 & 0 \\ \frac{1}{2} & \frac{1}{2} & 0 \\ \hline & 0 & 1 \end{tabular}
How can I do that? ★ → Airon 90 13:29, 14 April 2018 (UTC)
@Airon90: I have been looking into doing the same thing. But I think it might actually be better to add a new property for Butcher's tableau. Then we can have both the numerical method as a formula and a tableau.
Theerinaceousone (talk) 05:35, 25 July 2020 (UTC)
According to [1], you can actually create tables using the following command:
\begin{array}{ccc} a & b & S \\ \hline 0 & 0 & 1\\0 & 1& 1\\1&0&1\\1&1&0 \\ \end{array}
Theerinaceousone (talk) 05:45, 25 July 2020 (UTC)
 @Theerinaceousone: I think that it is better to insert A, b and c separately as formulas (applies to part (P518) RungeKutta matrix (Q97664752), RungeKutta weights vector (Q97664754), RungeKutta nodes vector (Q97664755) respectively) ★ → Airon 90 09:27, 25 July 2020 (UTC)
 @Airon90: I wouldn't be opposed to entering A, b, and c separately, but I don't see the advantage. What do you see as the upside of separating them? If we do separate them, I would want there to be some way of displaying in the standard Butcher tableau format. Also, I made a Butcher tableau property proposal yesterday [2]. Perhaps we should move this discussion there? Theerinaceousone (talk) 21:30, 25 July 2020 (UTC)
 @Airon90: Another idea, I just had, was that we could add a property <Butcher tableau> and then use has part (P527): RungeKutta matrix (Q97664752), RungeKutta weights vector (Q97664754), RungeKutta nodes vector (Q97664755) as a qualifiers. Theerinaceousone (talk)
Expand the scope to every mathematical conceptEdit
Notified participants of WikiProject Mathematics
Currently, the description of this property says that it can be used only for theorem and laws statements. Why not for mathematical concept definitions in general? For example, for something like this:
.Malore (talk) 00:27, 13 June 2018 (UTC)
 De facto it is already used this way in more than 50%. Maybe we need a new property for definition formulars. Bigbossfarin (talk) 10:09, 13 June 2018 (UTC)
 Support broadening the definition of this property to reflect usage (which has been that way a long time!) ArthurPSmith (talk) 18:02, 15 June 2018 (UTC)
 There is a general problem with the datatype. It can't be reliably queried on query server. Maybe we should try to find another working solution.
 Jura 09:24, 17 June 2018 (UTC)
 What kind of queries are you interested in? Spqrql is quite powerful. See for example meaning of identifiers in ideal gas law – The preceding unsigned comment was added by [[User:?]] ([[User talk:talk]] • contribs).
 The need for contributors is fairly simple: one needs to be able the retrieve the current value as entered through Wikidata query server.
 Jura 12:06, 17 June 2018 (UTC) The security philosphy is that the original source code is not shared, despite in its original context. Only a secure version which can be used as input is availible from the query service. I would be keen to learn for which usecase the original source code would be required. Physikerwelt (talk) 17:33, 17 June 2018 (UTC)
 The need for contributors is fairly simple: one needs to be able the retrieve the current value as entered through Wikidata query server.
 What kind of queries are you interested in? Spqrql is quite powerful. See for example meaning of identifiers in ideal gas law – The preceding unsigned comment was added by [[User:?]] ([[User talk:talk]] • contribs).
Formatting of vector quantitiesEdit
How should we format vector quantities? In school I used to draw arrows over vector quantities, probably because this is easiest when using a pen (compared to drawing a boldface letter). For defining formula I have seen both boldface and a vector arrow. Should we standardize on one particular format (for quantities used in mechanics, electromagnetism, ...)? I have entered all new formulas using boldface, following ISO/IEC 80000 (Q568496). I like this most (but could be convinced otherwise). Any other preference? Toni 001 (talk) 12:33, 18 December 2019 (UTC)
 I prefer bold to arrows. ArthurPSmith (talk) 20:03, 18 December 2019 (UTC)
 I have the same feelings as you, Toni. But I suppose arrows are more universal (also for schoolers) and more understandable. Infovarius (talk) 08:58, 19 December 2019 (UTC)
 I could imagine that in handwriting the arrow is preferred because it is easier to draw an arrow over a letter than to "write" a bold symbol. Toni 001 (talk) 10:28, 11 November 2020 (UTC)
 I agree with using bold over arrows for typset vectors. I've seldom seen arrow notation used in print.— The Erinaceous One 🦔 08:55, 12 November 2020 (UTC)
 I could imagine that in handwriting the arrow is preferred because it is easier to draw an arrow over a letter than to "write" a bold symbol. Toni 001 (talk) 10:28, 11 November 2020 (UTC)
Single value constraintEdit
defining formula (P2534) has a single value constraint (Q19474404). I think in general that this is good. However, different sources (or even different parts of the same source) might give different definitions for the same quantity, as is the case for wavenumber (Q192510): . I think it is important to find a way to store each definition, and have each sourced properly. The source requirement precludes dumping all definitions into the same line (x = definition 1 = definition 2) as one would not know which definition is stated in which source. In addition, some quantities are not simply defined as thing = definition, but appear inside a formula (that is, not simply on the left hand side), as is the case for magnetic flux density (Q30204).
This seems to suggest that in some cases we might want to violate the single value constraint.
However, there is an additional problem: To really explain the formula, we should first have a statement my item in defining formula (P7235) my symbol to state which symbol is used in the formula to define my item. Then we should have further statements involving calculated from (P4934) with in defining formula (P7235) as qualifier to explain which other quantities appear in the formula and which symbols are used for those quantities. This gets somewhat messy when there is more than one defining formula; one might be forced to use nonstandard symbol names in some defining formula to avoid conflicts with another formula.
The latter might seem to suggest that we should have one item for each formula. But this is probably not what we should do if the definitions are equivalent, because then they describe the same concept and deserve only one item. But we should definitely have all definitions  even if equivalent  so that someone coming from one area of science can work with what they are familiar with.
This is a though problem that I've been wondering about for the last few month. If you have any suggestions, then let's discuss. Toni 001 (talk) 11:57, 29 December 2019 (UTC)