Property talk:P7235

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in defining formula
any symbol used in the defining formula (P2534)

Represents	variable (Q50701)
Data type	Mathematical expression
Usage notes	add one statement as main value for each symbol appearing in any defining formula (P2534); for each symbol add a qualifier "symbol represents" (P9758)
Example	According to this template: f-number (Q862169) defining formula (P2534) $N={\frac {f}{D}}$ f-number (Q862169) in defining formula (P7235) $N$ f-number (Q862169) calculated from (P4934) focal length (Q193540) in defining formula (P7235) ${f}$ f-number (Q862169) calculated from (P4934) diameter of the entrance pupil (Q63572027) in defining formula (P7235) ${D}$ According to statements in the property: f-number (Q862169) → $N$ magnetic flux density (Q30204) → $\mathbf {B}$ When possible, data should only be stored as statements
See also	defining formula (P2534), symbol represents (P9758), quantity symbol (LaTeX) (P7973)
Lists	Items with the most statements of this property Count of items by number of statements (chart) Items with the most statements Items with the fewest statements Count of items by number of sitelinks (chart) Items with the most sitelinks Items with the most sitelinks, but no link to one Wikipedia (sample: Welsh Wikipedia, cywiki) Items with the fewest sitelinks Most linked wikis Items with the most identifier properties Items with no other statements Most recently created items Items with novalue claims Items with unknown value claims Usage history (total) Usage history (main statement) Chart by item creation date Database reports/Constraint violations/P7235 Map Random list
Proposal discussion	Proposal discussion
Current uses	Total 6,878 Main statement 6,647 96.6% of uses Qualifier 230 3.3% of uses Reference 1 <0.1% of uses

[create Create a translatable help page (preferably in English) for this property to be included here]

Item “defining formula (P2534)”: Items with this property should also have “defining formula (P2534)”. (Help)

Exceptions are possible as rare values may exist. Exceptions can be specified using exception to constraint (P2303).
List of violations of this constraint: Database reports/Constraint violations/P7235#Item P2534, SPARQL

Scope is as main value (Q54828448), as qualifier (Q54828449): the property must be used by specified way only (Help)

Exceptions are possible as rare values may exist. Exceptions can be specified using exception to constraint (P2303).
List of violations of this constraint: Database reports/Constraint violations/P7235#Scope, SPARQL

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. Exceptions can be specified using exception to constraint (P2303).
List of violations of this constraint: Database reports/Constraint violations/P7235#Entity types

Qualifiers “symbol represents (P9758)”: this property should be used only with the listed qualifiers. (Help)

Exceptions are possible as rare values may exist. Exceptions can be specified using exception to constraint (P2303). Known exceptions: module (Q18848)
List of violations of this constraint: Database reports/Constraint violations/P7235#allowed qualifiers, SPARQL

Required qualifier “symbol represents (P9758)”: this property should be used with the listed qualifier. (Help)

Exceptions are possible as rare values may exist. Exceptions can be specified using exception to constraint (P2303).
List of violations of this constraint: Database reports/Constraint violations/P7235#mandatory qualifier, SPARQL

Relationship to has-part

From the propoerty creation discussion:

• To bo honest, I do not really understand the proposal. How does it compare to the has part annotations that are used for example in https://www.wikidata.org/wiki/Q35875?--Physikerwelt (talk) 17:29, 3 June 2019 (UTC)
  • I'm not sure. Use of has part(s) (P527) on items with defining formula (P2534) seems pretty random. There are currently 97 items on [1]: they don't appear to be structured. It might work on one or the other item when reading the statement 1-by-1 and knowing in advance what to look for. Also, the proposal might not be suitable for every item about physics. --- Jura 11:30, 6 June 2019 (UTC)
  • It is still uncelar to me. Should I abandon using has-part Annotations Like in https://www.wikidata.org/wiki/Q35875 I think the has-part form is easyer to query and will be availible for annotations in Wikipedia soon https://phabricator.wikimedia.org/T208758. --Physikerwelt (talk) 13:17, 1 September 2019 (UTC)

Label

Using 'symbol' in labels is a better option. When I first saw this property, I didn't know what it was about. Wostr (talk) 14:27, 26 April 2020 (UTC)

 Support I also like more "symbol in defining formula". One might argue that "short is good", but in this case clarity might help. Toni 001 (talk) 18:14, 26 April 2020 (UTC)

• I don't think the property is meaningful without defining formula (P2534), especially, it shouldn't be used without a P2534 being present.

At some point we should be able to do a complex constraint that ensures the value of this property is present in P2534 (e.g. "words" at Q91798342#Q91798342$8ae98ac0-4309-6712-81f7-74c4b584cb1b in Q91798342#P2534).

If there are no parts of P2534-values that aren't covered by the proposed change, please go ahead. --- Jura 07:51, 27 April 2020 (UTC)

e.g. at Poisson's ratio (Q190453) we need to make sure that this property isn't confused with quantity symbol (LaTeX) (P7973) also present there. --- Jura 08:00, 27 April 2020 (UTC)

Yes. For new users we could state somewhere prominently that:

1. quantity symbol (LaTeX) (P7973) contains any symbol typically used for a given quantity
2. in defining formula (P7235) contains exactly one symbol, namely, the one used in the defining formula (P2534)

(This should be clear from the current label and description, but new users could miss this fine distinction.) Toni 001 (talk) 09:43, 27 April 2020 (UTC)

I added some usage instructions. Toni 001 (talk) 09:55, 27 April 2020 (UTC)

I wouldn't really count on people reading that. It was meant for a feature that was never implemented. In the meantime, property descriptions can be used. For properties, there is a risk that people already don't read that. --- Jura 05:38, 28 April 2020 (UTC)

Thanks for the hint about the non-implemented feature. I had noticed the mention of it in the description of Wikidata usage instructions (P2559) and was wondering what it meant. (By the way, I'm not too worried about "people not reading the instructions". This might happen for some casual user passing by, but once they start seriously contributing they'll need and find that information and be happy that it's there.) Toni 001 (talk) 08:42, 28 April 2020 (UTC)

Tighter constraints and symbol represents (P9758)-migration

I've been migrating the explanation of variables according to https://www.wikidata.org/wiki/Property_talk:P2534#How_to_explain_variables over the past weeks. While there is still a lot to do, I took the liberty of tightening the constraints on this property (in defining formula (P7235)) so that finding cases which need a migration can more easily be discovered and other editors be nudged into the right direction. Toni 001 (talk) 08:50, 8 September 2021 (UTC)

• It seems you changed some that can actually use "calculated from". Please clean up the incorrect changes. --- Jura 10:18, 7 November 2021 (UTC)

  There's been a long discussion before the creation of symbol represents (P9758), with the intent to move away from both "has part" and "calculated from". Please do not undo that work. Toni 001 (talk) 10:33, 7 November 2021 (UTC)

  • Apparently that was proposed for cases where "calculated from" isn't possible and there is no consensus to undo our work with "calculated from". --- Jura 10:50, 7 November 2021 (UTC)

    The motivation for symbol represents (P9758) was to unify the different ways in which formula variables are explained. Toni 001 (talk) 18:08, 7 November 2021 (UTC)

• As @Infovarius: mentioned in the discussion, this moves the main information from statement values to qualifiers. I agree with him that this doesn't make much sense or at least seems counterintuitive. Maybe the new "P9758" could be used as main value in cases where "calculated from" isn't possible (labeled, e.g. "composed from"). This could solve the problems with "part of" while mostly maintaining the structure we built before.

The approach attempted at Q604008#P7235 would mean that Wikidata would drop its usual way of modeling merely because of the presence of a defining formula.

Similar we wouldn't re-organize an item around sub-images because someone added a image (P18) to it.

Alternatives could be to host the defining formulas in separate items (either on Wikidata itself or elsewhere), given the technical problems around the datatype don't seem to be resolved. Commons now allows to annotate images directly.

@Arbnos: you didn't comment on either aspect in the discussion. Would you be ok with the use of "calculated from" and P9758 as main value? --- Jura 14:26, 7 November 2021 (UTC)

Inverse : when a math property has a distinct item, and the object it is about its own

Opensofias
Tobias1984
Arthur Rubin
Cuvwb
TomT0m
Physikerwelt
Lymantria
Bigbossfarin
Infovarius
Helder
PhilMINT
Malore
Lore.mazza51
Wikisaurus
The Anome
The-erinaceous-one
Daniel Mietchen
Haansn08
Xenmorpha
John Samuel
Jeremy Dover
Toni 001
Bocardodarapti
Duckmather
HTinC23
fgnievinski

Notified participants of WikiProject Mathematics

In the example Jensen's inequality (Q518131) I think it’s OK to link to the kind of function it is true for real-valued function of a real variable (Q3075263) with has quality Search

⟨ real-valued function of a real variable (Q3075263)    ⟩ has quality Search ⟨ 518131 ⟩

The statement would be a perfect place to link the variable described … however

⟨ real-valued function of a real variable (Q3075263)    ⟩ has quality Search ⟨ 518131 ⟩
in defining formula (P7235) ⟨ f ⟩

this is not enough to not trigger the constraint that a formula must have a symbol for the object defined.

What could we do ? author  TomT0m / talk page 16:36, 12 March 2022 (UTC)

The variables should be explained on the same item on which the formula is stated. Toni 001 (talk) 10:05, 13 March 2022 (UTC)

@Toni 001 That’s my point, actually, there is no way right now to explain the variable in the formula item. author  TomT0m / talk page 19:22, 15 March 2022 (UTC)

I'm not sure I follow: The item with the formula is Jensen's inequality (Q518131), and it could have a statement like this:

Jensen's inequality (Q518131)in defining formula (P7235)fsymbol represents (P9758)convex function (Q319913)

Side note: I find the use of has characteristic (P1552) problematic, at least from the examples I've seen so far. It seems to be used in ways which would be better handled by a dedicated (and properly discussed) property. Toni 001 (talk) 08:39, 16 March 2022 (UTC)

What about a qualifier to express the origin of the symbol?

In statements about the symbols used in a formula, we so far express what they stand for, via symbol represents (P9758). We could also express where the symbol comes from, e.g. the $\mu _{\mathrm {B} }$ in the in defining formula (P7235) statement for chemical affinity (Q382783) is derived from Μ (Q9902) and B (Q9705). Is this something we should be doing? If so, is there some recommended way of doing it? Thanks for any pointers. Daniel Mietchen (talk) 11:43, 7 September 2023 (UTC)