Property talk:P2442

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conversion to standard unit
translation of the value of a measurement to different units

Description	translation of a measurement to a different unit
Represents	conversion factor between units (Q110682638)
Data type	Quantity
Domain	According to this template: items for units According to statements in the property: unit of measurement (Q47574) When possible, data should only be stored as statements
Allowed values	number with standard units (note: this should be moved to the property statements)
Allowed units	Instances of: unit of measurement
Usage notes	Use P2370 for conversion to SI base or derived units.
Example	yard (Q482798) → 3 foot foot (Q3710) → 12 inch line (Q649848) → 10 tochka sazhen (Q2018709) → 3 arshin
Tracking: usage	Category:Pages using Wikidata property P2442 (Q26678446)
See also	conversion to SI unit (P2370), subdivision of this unit (P9059)
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 Database reports/Constraint violations/P2442 Map Random list
Proposal discussion	Proposal discussion
Current uses	Total 2,176 Main statement 2,171 99.8% of uses Qualifier 5 0.2% of uses

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

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/P2442#Type Q47574, 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/P2442#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/P2442#Entity types

Qualifiers “Wikidata usage instructions (P2559), valid in place (P3005), start time (P580), end time (P582), 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/P2442#allowed qualifiers, SPARQL

Conflicts with “instance of (P31): currency (Q8142)”: 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/P2442#Conflicts with P31, SPARQL

This property is being used by: ca:Plantilla:Infotaula d'unitat, ca:Plantilla:Infotaula unitat eu:Txantiloi:Unitate infotaula ga:Teimpléad:WD Bosca Sonraí Aonad Please notify projects that use this property before big changes (renaming, deletion, merge with another property, etc.)

Obtaining the output type when converting

The UI shows which units the various conversion factors correspond to. Where does that data come from? It isn't clear from querying the value of the property.

The datatype of the conversion factors are simply xsd:decimal.

@Drrngrvy: The following query retrieves both magnitude and unit for the example of {{Q:79738}}:

select * where {
  # gigabyte
  wd:Q79738 p:P2442 / psv:P2442 [
    wikibase:quantityAmount ?amount ;
    wikibase:quantityUnit ?unit ;
  ] .
  ?unit rdfs:label ?unitLabel .
    filter (lang(?unitLabel) = "en")
}

Try it!

Toni 001 (talk) 18:12, 19 October 2019 (UTC)

Scope: Which conversion to include, and which not.

I'd like to better understand and define what the property could and should be used for, and what not. Background: I recently removed some conversions from say, light-years, kilometres, ... to, say, microinches, historical nautical miles, metres, ... . Those removals were motivated by different reasons, or a combination:

1. conversion was wrong (missing a couple of 000, which can happen if someone enters very large or small numbers manually)
2. conversion is already given as conversion to SI unit (P2370)
3. conversion was to an item representing different units ("general topic about unit XYZ")
4. conversion was from more-standard to less-standard

• #1 seems uncontroversial. If there is a credible source for the wrong value, then the statement could be kept but deprecated.
• #2 is justified by the usage message: "Use P2370 for conversion to SI base or derived units."
• #3 can be justified by semantic consistency: Topics / collections of different units on the one hand, and a particular unit, used in a certain geographical region in a certain time period, with one particular value on the other hand, are different concepts. They each deserve a separate item, with their type-specific set of properties.
• #4 could be read from the label of this property: Even though unit conversions are "symmetric" in the sense that one can convert back and forth, this property does not need to convert both "byte to gigabyte" and "gigabyte to byte". The last one is sufficient to establish a relation, from which other conversions can be derived.

Especially for the last point (#4) I'd like to collect possible use cases of this property. Analyzing them and listing the possible ways in which they can be solved might help us come to a consensus about how to use this property. Toni 001 (talk) 14:44, 5 October 2019 (UTC)