Property talk:P2370

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conversion to SI unit
conversion of the unit into a coherent SI unit

Represents	coherent SI unit (Q69197847), conversion factor between units (Q110682638)
Data type	Quantity
Domain	According to this template: items for units that don't have instance of (P31) or subclass of (P279) = unit without standard conversion to SI (Q21684377), i.e. unit or class of units that can have various definitions and can't be converted to SI units with a single conversion factor. If some of the units in this class can be converted to SI units, specific items should be made for them. According to statements in the property: unit of measurement (Q47574) When possible, data should only be stored as statements
Allowed values	number with SI base units/SI derived units (note: this should be moved to the property statements)
Allowed units	Instances of: coherent SI unit metre (Q11573), kilogram (Q11570), second (Q11574), ampere (Q25272), ohm (Q47083), volt (Q25250), kelvin (Q11579), mole (Q41509), candela (Q83216), square metre (Q25343), newton (Q12438), newton metre (Q215571), joule (Q25269), cubic metre (Q25517), pascal (Q44395), metre per second (Q182429), metre per square second (Q1051665), kilogram per cubic metre (Q844211), hertz (Q39369), watt (Q25236), cubic metre per second (Q794261), joule per mole (Q13035094), tesla (Q163343), candela per square metre (Q281096), becquerel (Q102573), weber (Q170804), joule per tesla (Q21088638), farad (Q131255), sievert (Q103246), coulomb (Q25406), radian (Q33680), pascal second (Q21016931), mole per cubic metre (Q2415352), katal (Q208634), henry (Q163354), steradian (Q177612), kilogram per mole (Q28924753), reciprocal metre (Q11547251), newton second (Q3395194), lumen (Q484092), square metre per second (Q3332099), kilogram per metre (Q25999243), farad per metre (Q21294882), ampere per square metre (Q2844477), radian per second (Q1063756), kilogram per square metre (Q25377184), coulomb metre (Q28739766), ampere per metre (Q2844478), lux (Q179836), reciprocal second (Q6137407), watt per steradian (Q16683188), joule per kilogram (Q57175225), joule per kelvin (Q21393312), joule per mole kelvin (Q20966455), newton per metre (Q26156113), cubic metre per mole (Q21615967), reciprocal cubic metre (Q21401573), metre per second to the fourth power (Q25381678), coulomb per square metre (Q68343206), siemens (Q169893), volt per metre (Q3562962), ampere per radian (Q30064202), radian per square second (Q30338333), radian per metre (Q30338605), metre kelvin (Q41588368), kilogram square metre (Q50808017), katal per cubic metre (Q69429606), watt per square metre steradian (Q69429226), gray per second (Q69428896), coulomb per cubic metre (Q69425409), joule per cubic metre (Q69424806), reciprocal mole (Q68712008), metre to the fourth power (Q67147153), metre to the power of six (Q67147817), joule second (Q1709783), watt per metre kelvin (Q1463969), gray (Q190095), volt ampere (Q550341), joule per kilogram kelvin (Q3085309), kilogram square metre per second (Q65665675), watt per square metre kelvin (Q3566738), newton per square ampere (Q21392882), cubic metre per kilogram square second (Q78336909), 1 (Q199), mole per second (Q85178038), watt per square metre hertz (Q95375885), watt per metre (Q96192470), kilogram per second (Q25381181), siemens square metre per mole (Q96309077), radian square metre per mole (Q96347486), radian square metre per kilogram (Q96347983), watt per square metre (Q3566737), mole per kilogram (Q88957663), joule per square metre (Q80374519), cubic metre per kilogram (Q3332095), ampere square metre (Q71581529), watt per kilogram (Q67060736), watt second (Q7974920), weber per metre (Q77899731), lumen second (Q910311), ohm metre (Q1441459), ampere second (Q65665809), joule per cubic metre kelvin (Q3186734), kelvin per watt (Q3194958), square metre kelvin per watt (Q3332092), ampere square metre per joule second (Q97540991), ampere second per kilogram (Q97541209), per tesla second (Q97543281), becquerel per kilogram (Q88768297), becquerel per cubic metre (Q98102832), becquerel per square metre (Q98103135), square metre per steradian (Q98266832), square metre per joule (Q98267267), square metre per steradian joule (Q98269780), square metre per mole (Q86203731), newton square metre per square kilogram (Q21395031), watt per kelvin (Q81663366), lumen per watt (Q83386886), kelvin metre per watt (Q84451486), square metre per kilogram (Q86200529), square pascal second (Q86897783), pascal second per cubic metre (Q87047886), pascal second per metre (Q87051580), kilogram per square metre second (Q92011107), joule per second (Q92711514), kelvin per pascal (Q93947085), newton per square metre (Q39469927), weber metre (Q71580762), per square metre second (Q83951055), per square metre second steradian (Q83855084), reciprocal henry (Q77996931), watt per square metre kelvin to the fourth power (Q21395834), joule per mole kelvin difference (Q69427692), joule per kilogram kelvin difference (Q69423273), joule per kelvin difference (Q68975544), reciprocal kelvin difference (Q79331235), reciprocal pascal (Q79104611), reciprocal farad (Q89992008), per second steradian (Q83853845), joule per metre (Q56023789), joule square metre per kilogram (Q98643033), square metre per volt second (Q98813401), per cubic metre second (Q98915792), kilogram metre per second (Q78775089), sievert per second (Q99605059), coulomb per kilogram second (Q99721917), coulomb per kilogram (Q28683485), ampere per volt metre (Q20966435), metre per cubic second (Q21719454), hertz per tesla (Q21095810), newton metre second (Q73429216), lumen per square metre (Q64833836), coulomb per mole (Q21396202), hertz per second (Q68582988), pascal per kelvin difference (Q79398638), siemens per metre (Q80842107), lux second (Q83620455), newton second per metre (Q87049028), kelvin difference per metre (Q92717607), reciprocal pascal second (Q100293463), volt second (Q100293891), watt per steradian metre (Q100294053), hertz per volt (Q101195156), watt per steradian square metre hertz (Q101434890), joule per square metre hertz (Q101435195), joule per cubic metre hertz (Q101460091), watt per hertz (Q101460900), watt per steradian hertz (Q101461942), kilogram per joule (Q101515303), newton per cubic metre (Q103419450), watt per cubic metre (Q104381302), volt-ampere second (Q107299736), square tesla metre per henry (Q105102274), henry per metre (Q55663153), metre second (Q105222377), cubic metre per coulomb (Q105267497), volt metre (Q83948162), second per cubic metre (Q105637361), reciprocal joule cubic metre (Q105687104), square volt per square kelvin (Q105728783), volt per kelvin (Q105761745), ampere per square metre square kelvin (Q105883158), kelvin difference (Q69363953), cubic metre per cubic metre (Q106629974), metre per radian (Q106639624), kilogram per kilogram (Q106645216), kilogram metre per square second (Q106645249), kilogram per metre second (Q106653452), reciprocal square second (Q106680668), kilogram square metre per square second (Q106681350), kilogram per metre square second (Q106681449), metre square second per kilogram (Q106682225), kilogram per square second (Q106682321), newton metre per second (Q106682414), kilogram square metre per cubic second (Q106682512), kilogram per metre square second kelvin (Q106688808), kilogram per cubic second (Q106688958), kilogram metre per cubic second kelvin (Q106689063), kilogram per cubic second kelvin (Q106689188), cubic second kelvin per kilogram (Q106689202), cubic second kelvin per kilogram square metre (Q106689216), kilogram square metre per cubic second kelvin (Q106689255), kilogram square metre per square second kelvin (Q106696962), square metre per square second kelvin (Q106697069), kilogram square metre per square second kelvin (Q106707404), square metre per square second kelvin (Q106725578), square metre per square second (Q106740890), metre square second kelvin per kilogram (Q106764292), joule per metre to the fourth power (Q106867426), kilogram per square metre square second (Q106867449), kilogram metre per cubic second (Q106880558), kilogram square metre per cubic second steradian (Q106880580), kilogram metre per cubic second steradian (Q106880609), newton metre per radian (Q106886160), kilogram per cubic second steradian (Q106900091), kilogram per metre cubic second steradian (Q106900318), kilogram per metre cubic second (Q106919394), candela steradian cubic second per kilogram square metre (Q106936862), candela steradian second (Q106947267), candela steradian (Q106947284), candela steradian per square metre (Q106947296), candela steradian second per square metre (Q106947331), reciprocal kelvin (Q107028673), square kilogram per square metre cubic second (Q107042276), kilogram per quartic metre second (Q107042351), kilogram square metre per square second mole (Q107095937), kilogram square metre per square second kelvin mole (Q107095987), kilogram square metre per square second kelvin mole (Q107096038), cubic second square ampere per kilogram cubic metre (Q107096164), cubic second square ampere per kilogram mole (Q107096193), per kilogram second (Q107222082), square second per kilogram (Q107222127), quartic metre per square second (Q107222165), square second ampere per kilogram (Q107222174), square metre per cubic second (Q107222188), ampere per kilogram (Q107222200), square second per kilogram quintic metre (Q107299304), kilogram cubic metre per cubic second square ampere (Q107299360), square kilogram quartic metre per sextic second square ampere square kelvin (Q107299411), cubic metre per second ampere (Q107299610), kilogram square metre per cubic second ampere (Q107299709), kilogram square metre per cubic second ampere kelvin (Q107305236), kilogram per square second ampere (Q107305389), joule per kelvin square metre square root second (Q107313937), pascal square root metre (Q107313969) or reciprocal square metre (Q11547252)
Usage notes	Use P2442 for conversions to non-SI units.
Example	millimetre (Q174789) → 0.001 metre inch (Q218593) → 0.0254 metre gram (Q41803) → 0.001 kilogram pascal (Q44395) → 1 pascal millimetre of mercury (Q6859652) → 133.322365 pascal
Tracking: usage	Category:Pages using Wikidata property P2370 (Q26250028)
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 Minimum and maximum Items with highest numeric value Items with lowest numeric value User:Laboramus/Units/P2370 (Units used) Database reports/Complex constraint violations/P2370 Database reports/Constraint violations/P2370 Map Random list
Proposal discussion	Proposal discussion
Current uses	Total 2,476 Main statement 2,470 99.8% of uses Qualifier 6 0.2% of uses

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

Units: “Q11573, Q11570, Q11574, Q25272, Q47083, Q25250, Q11579, Q41509, Q83216, Q25343, Q12438, Q215571, Q25269, Q25517, Q44395, Q182429, Q1051665, Q844211, Q39369, Q25236, Q794261, Q13035094, Q163343, Q281096, Q102573, Q170804, Q21088638, Q131255, Q103246, Q25406, Q33680, Q21016931, Q2415352, Q208634, Q163354, Q177612, Q28924753, Q11547251, Q3395194, Q484092, Q3332099, Q25999243, Q21294882, Q2844477, Q1063756, Q25377184, Q28739766, Q2844478, Q179836, Q6137407, Q16683188, Q57175225, Q21393312, Q20966455, Q26156113, Q21615967, Q21401573, Q25381678, Q68343206, Q169893, Q3562962, Q30064202, Q30338333, Q30338605, Q41588368, Q50808017, Q69429606, Q69429226, Q69428896, Q69425409, Q69424806, Q68712008, Q67147153, Q67147817, Q1709783, Q1463969, Q190095, Q550341, Q3085309, Q65665675, Q3566738, Q21392882, Q78336909, Q199, Q85178038, Q95375885, Q96192470, Q25381181, Q96309077, Q96347486, Q96347983, Q3566737, Q88957663, Q80374519, Q3332095, Q71581529, Q67060736, Q7974920, Q77899731, Q910311, Q1441459, Q65665809, Q3186734, Q3194958, Q3332092, Q97540991, Q97541209, Q97543281, Q88768297, Q98102832, Q98103135, Q98266832, Q98267267, Q98269780, Q86203731, Q21395031, Q81663366, Q83386886, Q84451486, Q86200529, Q86897783, Q87047886, Q87051580, Q92011107, Q92711514, Q93947085, Q39469927, Q71580762, Q83951055, Q83855084, Q77996931, Q21395834, Q69427692, Q69423273, Q68975544, Q79331235, Q79104611, Q89992008, Q83853845, Q56023789, Q98643033, Q98813401, Q98915792, Q78775089, Q99605059, Q99721917, Q28683485, Q20966435, Q21719454, Q21095810, Q73429216, Q64833836, Q21396202, Q68582988, Q79398638, Q80842107, Q83620455, Q87049028, Q92717607, Q100293463, Q100293891, Q100294053, Q101195156, Q101434890, Q101435195, Q101460091, Q101460900, Q101461942, Q101515303, Q103419450, Q104381302, Q107299736, Q105102274, Q55663153, Q105222377, Q105267497, Q83948162, Q105637361, Q105687104, Q105728783, Q105761745, Q105883158, Q69363953, Q106629974, Q106639624, Q106645216, Q106645249, Q106653452, Q106680668, Q106681350, Q106681449, Q106682225, Q106682321, Q106682414, Q106682512, Q106688808, Q106688958, Q106689063, Q106689188, Q106689202, Q106689216, Q106689255, Q106696962, Q106697069, Q106707404, Q106725578, Q106740890, Q106764292, Q106867426, Q106867449, Q106880558, Q106880580, Q106880609, Q106886160, Q106900091, Q106900318, Q106919394, Q106936862, Q106947267, Q106947284, Q106947296, Q106947331, Q107028673, Q107042276, Q107042351, Q107095937, Q107095987, Q107096038, Q107096164, Q107096193, Q107222082, Q107222127, Q107222165, Q107222174, Q107222188, Q107222200, Q107299304, Q107299360, Q107299411, Q107299610, Q107299709, Q107305236, Q107305389, Q107313937, Q107313969, Q11547252”: value unit must be one of listed. (Help)

Exceptions are possible as rare values may exist. Exceptions can be specified using exception to constraint (P2303). Known exceptions: degree Celsius (Q25267), degree Fahrenheit (Q42289), degree Rankine (Q37732658)
List of violations of this constraint: Database reports/Constraint violations/P2370#Units

Type “unit of measurement (Q47574)”: item must contain property “instance of (P31)” with classes “unit of measurement (Q47574)” or their subclasses (defined using subclass of (P279)). (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/P2370#Type Q47574, SPARQL

Conflicts with “instance of (P31): unit without standard conversion to SI (Q21684377)”: this property must not be used with the listed properties and values. (Help)

List of violations of this constraint: Database reports/Constraint violations/P2370#Conflicts with P31, hourly updated report, SPARQL

Single value: this property generally contains a single value. (Help)

Exceptions are possible as rare values may exist. Exceptions can be specified using exception to constraint (P2303). Known exceptions: stadion (Q1645966), pous (Q7235735), square plethron (Q25909383), pechys ephtymetrikos (Q25915550), square cubit (Q25932175), Kotyla (Q2559410), Tokyo Dome (Q11524325)
List of violations of this constraint: Database reports/Constraint violations/P2370#Single value, SPARQL

Item “measured physical quantity (P111)”: Items with this property should also have “measured physical quantity (P111)”. (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/P2370#Item P111, SPARQL

Qualifiers “defining formula (P2534)”: 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).
List of violations of this constraint: Database reports/Constraint violations/P2370#allowed qualifiers, SPARQL

Conflicts with “length (P2043)”: this property must not be used with the listed properties and values. (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/P2370#Conflicts with P2043, SPARQL

Conflicts with “mass (P2067)”: this property must not be used with the listed properties and values. (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/P2370#Conflicts with P2067, SPARQL

Scope is as main value (Q54828448): 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/P2370#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/P2370#Entity types

Property missing?
TODO: if applicable, add conversion to standard unit (P2442) or instance of (P31)=unit without standard conversion to SI (Q21684377) or define exceptions (Help)
Violations query: SELECT ?item ?itemLabel ?count WITH { SELECT ?item (COUNT(DISTINCT ?st) as ?count) { ?st wikibase:quantityUnit ?item . FILTER(?item != wd:Q199) MINUS { ?item wdt:P31 wd:Q8142 } MINUS { ?item wdt:P2370 [] } MINUS { ?item wdt:P31 wd:Q21684377 } } GROUP BY ?item HAVING(?count > 24) } as %inc1 WHERE { INCLUDE %inc1 FILTER ( ?item != wd:Q550207 ) FILTER ( ?item not in ( wd:Q5 , wd:Q319604 , wd:Q11229 , wd:Q181011 ) ) SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". } } ORDER BY DESC(?count) LIMIT 150
List of this constraint violations: Database reports/Complex constraint violations/P2370#Property missing?

⚠️ Mandatory: Check units
⚠️ Mandatory, no exception. Please use conversion to standard unit (P2442) for other conversion. (Help)
Violations query: SELECT ?item ?unit WHERE { ?item p:P2370/psv:P2370/wikibase:quantityUnit ?unit. MINUS { VALUES ?unitsSI { wd:Q223662 wd:Q208469 }. ?unit wdt:P31 ?unitsSI. }. MINUS { ?unit wdt:P2370 []. } }
List of this constraint violations: Database reports/Complex constraint violations/P2370#⚠️ Mandatory: Check units

This property is being used by: ca:Plantilla:Infotaula d'unitat, ca:Plantilla:Infotaula unitat eu:Txantiloi:Unitate infotaula q:it:Template:Wikidata/man b:it:Template:Wikidata/man ga:Teimpléad:WD Bosca Sonraí Aonad be-tarask:Шаблён:Фізычная велічыня Please notify projects that use this property before big changes (renaming, deletion, merge with another property, etc.)

Sample conversion query

• Items used: nautical mile (Q93318)   

• Properties used: lighthouse range (P2929)   , conversion to SI unit (P2370)   

SELECT
  ?item ?itemLabel 
  ?inputvalue ?inputunit ?inputunitLabel ?convinput
  ?outputvalue ?outputunit ?outputunitLabel ?convoutput
{
    BIND( wd:Q93318 as ?outputunit )
    ?item p:P2929 /psv:P2929 [ wikibase:quantityAmount ?inputvalue ; wikibase:quantityUnit ?inputunit ] . 
    ?inputunit p:P2370/psv:P2370 [ wikibase:quantityAmount ?convinput ; wikibase:quantityUnit ?siunit ]  .             
    ?outputunit p:P2370/psv:P2370 [ wikibase:quantityAmount ?convoutput ; wikibase:quantityUnit ?siunit ] .
    BIND( ROUND( ?inputvalue * ?convinput / ?convoutput * 1000 )/1000 as ?outputvalue ) .
    SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
}  
ORDER BY DESC(?outputvalue)
LIMIT 50

Try it!

Discussion

higher powers, composition of base units

Can this property be used for units where a base unit is raised to a certain power (for example, using square metre (Q25343) and cubic metre (Q25517) on area and volume units)? Can it be used for derived units when a similar unit containing only base units is given (for example, some unit which ultimately is expressible in cubic metre per second (Q794261))? Mahir256 (talk) 22:40, 4 December 2015 (UTC)

It would make sense. Let's do that. --- Jura 23:39, 4 December 2015 (UTC)

Graphics from former unique value constraint

• +0.000000000000000000000001: yoctometre (Q3221356), zeptogram (Q6171168)
• +0.000000000000000001: femtogram (Q1913097), attosecond (Q2483628), attometre (Q6003257)
• +0.000000000000001: femtometre (Q208788), picogram (Q3239557)
• +0.000000000001: picometre (Q192274), nanogram (Q2282906)
• +0.000000001: nanometre (Q178674), nanosecond (Q838801), microgram (Q1645498), microlitre (Q2282891)
• +0.000001: micrometre (Q175821), microsecond (Q842015), cubic centimetre (Q1022113), millilitre (Q2332346), milligram (Q3241121), milligram per cubic metre (Q21077820)
• +0.00001: dyne (Q201933), centilitre (Q1815100)
• +0.001: litre (Q11582), gram (Q41803), millimetre (Q174789), millisecond (Q723733), gram per cubic metre (Q21604951)
• +0.01: centimetre (Q174728), decagram (Q6517513)
• +0.1: decimetre (Q200323), hectogram (Q1057069), hectolitre (Q2029519)
• +1: kilogram (Q11570), metre (Q11573), second (Q11574), kelvin (Q11579), newton (Q12438), watt (Q25236), degree Celsius (Q25267), joule (Q25269), ampere (Q25272), square metre (Q25343), cubic metre (Q25517), hertz (Q39369), mole (Q41509), pascal (Q44395), candela (Q83216), metre per second (Q182429), newton metre (Q215571), cubic metre per second (Q794261), gram per litre (Q834105), kilogram per cubic metre (Q844211), joule per mole (Q13035094)
• +10: decametre (Q848856), deciare (Q22350885)
• +100: are (Q185078), hectometre (Q844338)
• +1000: tonne (Q191118), kilometre (Q828224), sthène (Q1793863), kilohertz (Q2143992), kilowatt (Q3320608), kilometre per second (Q4220561), kilojoule (Q4989854), megagram (Q11776930), gram per cubic centimetre (Q15639371), kilopascal (Q21064807), decare (Q22350887)
• +10000: hectare (Q35852), myriametre (Q1970718)
• +1000000: square kilometre (Q712226), megahertz (Q732707), megametre (Q1054140), gigagram (Q2799294), megawatt (Q6982035), megajoule (Q14786969), megapascal (Q21062777)
• +1000000000: gigametre (Q854546), teragram (Q1770733), gigahertz (Q3276763), cubic kilometre (Q4243638)
• +1000000000000: petagram (Q2612219), terametre (Q3267417)
• +1000000000000000: exagram (Q2655272), petametre (Q3277919)
• +1000000000000000000: exametre (Q3277907), zettagram (Q14754979)
• +1000000000000000000000: yottagram (Q613726), zettametre (Q3277915)
• +3600: hour (Q25235), watt hour (Q12874593)

Confusion

I think this property is quite confusing Normally SI base units are:

This property works fine, for all units that can be multiplied by a number to derive at a standard SI unit, but is not useful for others.

It works fine for almost all units used at Wikidata so nothing really confusing about it. You may want to edit the German label to match the current English one rather than to change that to something different.
--- Jura 05:27, 4 May 2016 (UTC)

Is this property appropriate when the conversion is not known exactly?

For example, Year is described as the orbital period. But there are several different kinds of orbital periods that fit the description, and each of these is slowly changing over time. --Jc3s5h (talk) 18:25, 19 September 2017 (UTC)

In some cases, such as year, semester, quarter..., we cannot give exactly conversion but I think that we can give some approximate conversion instead of giving non-exactly conversion. So do we have any appropriate conversion property which is represented for such cases? Phucnt.nii (talk) 06:42, 20 September 2017 (UTC)

• Please use conversion to standard unit (P2442) if no exact conversion is known. If an item also covers variants of units that have an exact conversion, please make a new item for the unit that can be converted.
  --- Jura 08:39, 1 October 2017 (UTC)

• Thanks, I've followed your advice for tropical year (Q189607), sidereal year (Q2281928), anomalistic year (Q2735933), and year (Q577) (all of which already existed). Jc3s5h (talk) 15:40, 1 October 2017 (UTC)

units missing from allowed units constraint

The ampere per meter and the ampere per square meter are missing from the allowed units constraint. —Eli355 (talk) 16:03, 29 August 2018 (UTC)

Additions to normalizations (notably on Wikidata Query Service)

See Wikidata:Contact_the_development_team#«_annum_»_conversion_?. --- Jura 18:02, 6 March 2020 (UTC)

Coherent SI units

I tried to make the label and description of this property more precise: What we really want to convert to are the coherent SI units.

• Why not just base units? Because we also want to convert km/h to m/s, which is not a base unit.
• Why coherent? Because this set of units is well defined withing the SI. For instance, m is, while cm, km, mm, µm are not. kg is, while g, mg and µm and not. m^3/kg is, while l/kg is not. Pa is, because it is just a different name for N/m^2, which is an alias for kg/(m s^2).

Most conversions stored in this property already target coherent SI units. There are a few outliers that we should fix. Outliers are for instance conversion to micrometer or liter, which should be stated as conversion to meter or cubic metre, respectively. (The original values can be preserved by moving them to conversion to standard unit (P2442).)

For the record, the proposed new label is "conversion to coherent SI unit" and the description is "equivalent quantity whose unit is a product of powers of SI base units". Let's discuss if they should be further improved. Toni 001 (talk) 18:34, 19 April 2020 (UTC)

Let's take some time to think this over. This property shouldn't be changed around lightly. It's primary function is to define unit conversion on query server. --- Jura 18:51, 19 April 2020 (UTC)

Hello @Jura1: One more point I could mention:

* Why not derived SI unit? Because all of kg, mg, µg, ng, ... are derived units, but only kg (the kilogram) is the coherent SI unit.

What I'm trying to achieve with this proposal is to state precisely and using technically correct terminology what the (presumably) intended use for this property is. With regard to conversion on the query server, this is exactly what triggered my investigation into this issue: When trying to rank values independent of the units in which they are entered, one tries to convert them to a common unit and then compares the numerical values. However, what is this common units? For units translatable to the SI, it is precisely the coherent units which have a unique conversion factor (in the sense that there is no coherent SI unit with a different conversion factor). If we did not make this restriction, then one length unit could, say, be converted to millimeters, and another one to kilometers. But then quantities given in those different length units would not be ordered by their actual length. By requiring coherent SI units we ensure that each is converted to meters before comparison. Toni 001 (talk) 21:04, 19 April 2020 (UTC)

Hello

Tobias1984
Snipre
Physikerwelt
Pamputt
Petermahlzahn
Jibe-b
Restu20
Daniel Mietchen
TomT0m
ArthurPSmith
Mu301
Sarilho1
SR5
DavRosen
Danmichaelo
Ptolusque
PhilMINT
Malore
Thibdx
Ranjithsiji
Niko.georgiev
Simon Villeneuve
Toni 001
Marc André Miron
DePiep
RShigapov
CarlFriedberg
Crocodilecoup
Mkomboti
Amorenobr (talk) 01:27, 3 August 2022 (UTC)
Valverde667 (talk) 16:07, 4 August 2022 (UTC)
fgnievinski

Notified participants of WikiProject Physics. I propose refine the scope of "conversion to SI unit" to "conversion to coherent SI unit". Please see explanation above. Thanks. Toni 001 (talk) 09:44, 20 April 2020 (UTC)

I like the general idea, but maybe there are some edge cases I haven't thought of that would be a problem. Jc3s5h (talk) 12:13, 20 April 2020 (UTC)

This seems reasonable to me, but I agree it should not be done hastily to give time to think of any problems that might occur. ArthurPSmith (talk) 14:50, 20 April 2020 (UTC)

Hello @Jc3s5h, ArthurPSmith: Sure, no need to hurry. I've been thinking about and preparing this for a year, so now I can take some time to explain the idea. For instance, one of my "maintenance" queries is this one: https://w.wiki/Nbk. It currently lists ~150 coherent SI units (together with links to other unit ontologies - WL and QUDT). Note that all the units listed under allowed units constraint are indeed coherent, as can be verified with the following query: https://w.wiki/Nbo. So, my proposal is already implemented because people were intuitively doing the right thing. Toni 001 (talk) 08:23, 21 April 2020 (UTC)

I don't understand the change: what is the definition of SI unit, coherent SI unit (I never heard about that term) and standard unit ? We can't change anything if we don't have the correct definition of the terms. regards Snipre (talk) 15:32, 20 April 2020 (UTC)

Hello @Snipre: Here is a quick summary (do let me know if you - or anybody - like more detail):

• SI base unit (Q223662): One of kg, m, s, A, K, mol, cd. 7 in total.
• coherent SI unit (Q69197847): Combine the base units using (positive or negative) powers, for instance, m^2, m^3, 1/m, ..., and products, for instance A s, m/s, kg/m^3, .... Some of those combinations have special names, like Pa (pascal). (They are instances of this class: SI unit with special name (Q68618328).) The base units are a special case of the coherent units.
• SI derived unit (Q208469): In addition to all the coherent units, now also allow adding an SI prefix (Q131299) to any unit in the expression. Examples: µm, km/s, ....
• SI unit (Q61610698): Any unit that is defined by the SI, that means, all the units described above.

Toni 001 (talk) 08:40, 21 April 2020 (UTC)

About standard unit: Some units are not (yet) part of the SI. For instance, information units like MB (megabyte). But we still want to store somewhere the statement that this is equivalent to 1000000 B (byte). That's what we use conversion to standard unit (P2442) for. Toni 001 (talk) 08:46, 21 April 2020 (UTC)

Hello. It's been a while now. I now think that it's fine to keep the current label (as labels can be under-specified), but that it would be good to improve the description. Given that the current description has already caused confusion (topic "Confusion" above) and that there's been no objection for a few month I'll go ahead and update just the description. Toni 001 (talk) 08:47, 19 July 2020 (UTC)