Talk:Q2111
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Autodescription — speed of light in vacuum (Q2111)
description: speed of electromagnetic waves in vacuum
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- Report on constraint conformation of “speed of light in vacuum” claims and statements. Constraints report for items data
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Instance and class of quantity[edit]
The vacuum speed of light can refer to two different concepts: The (physical) quantity and its particular value (299792458 m/s). I created item speed of light in vacuum (Q80170850) for the former. This is a subtle difference but having two items allows having consistent sets of properties for quantities on the one hand, and individual quantities on the other. Toni 001 (talk) 10:43, 29 December 2019 (UTC)
- Probably related to Talk:Q1924249. --Infovarius (talk) 23:00, 30 December 2019 (UTC)
- Yes, related. The point of that discussion was to clarify how in general quantities and particular quantities map to the Wikidata ontology. And here we have the curious case where one name refers to either an instance or a class. Toni 001 (talk) 00:31, 31 December 2019 (UTC)
- I realized that the practice of creating a quantity class for each physical constant (individual quantity) might not be necessary. Therefore I merged Q80170850 into Q2111. There are some consequences for modeling quantities that might require updating some property constraints. For instance, any (instance of) physical constant (Q173227) might have properties that are typically used for quantity kinds (subclasses of physical quantity (Q107715)), for instance quantity symbol (string) (P416), ISQ dimension (P4020), .... Sometimes physical constants are used as units, and therefore will have a unit symbol (P5061). That means, one item having both quantity and unit symbol which is currently a constraint violation. Toni 001 (talk) 10:41, 22 February 2020 (UTC)