query-acb43ec8b78c40e10786a986d22df3f0
Coherent SI units or simply ask here. ISO/IEC 80000 standard series and the SI brochureHello. I've been improving quantities and units in Wikidata for 1.5 years now, making it more consistent and standard compliant and adding more data. While doing that I learned a lot. Therefore I though I'd share some of the motivation and give an overview of some aspects and the progress so far. Some of this is pretty technical and a casual user of units might not be aware (and does not need to be). For more details on the technical aspects see Quantities and the units in which those quantities are expressed are the basic building block of quantitative science and communication. To unambiguously transfer the statements that a study determined the value of quantity X expressed in unit Y one needs unambiguous identifiers for those concepts. There are various ontologies which provide identifiers for quantities and units. Wikidata is one of them and also links to the others using external identifier properties. . reciprocal kelvin whose recommended unit of measurement is the linear expansion coefficientAn example quantity is the one). linearNote how in this phase I linked to the respective Q-IDs to make it clear exactly which concept I was referring to. This facilitates correct translation (by humans and machines alike) of this sentence into other languages (note how there are multiple "expansion coefficients" - here we mean the In Wikidata we currently have about 800 quantities and 1700 units which are "notable" in that they are linked to other ontologies, thereby fixing their precise meaning. . This makes the coherent SI units the most important set of all units. inch. Non-SI units also have conversions to coherent SI units, like the 1 km is 1000 m: For instance, (P2370)conversion to SI unit (k, m, μ and so on). The units derived using prefixes are related to the coherent ones by the property SI prefixes, for instance N (newton) is a special name for kg m/s² (all SI units with special name are coherent). From the coherent SI units all the other SI units can be derived by inserting units that received a special name. For instance, dividing m (metre) and s (second) one gets m/s (metre per second), the unit of speed. Then there are certain SI base units. The coherent SI units are those formed by multiplying and dividing the 7 coherent SI units. Those can be further restricted to the SI units, which include SI-accepted unitsAn important subset of those units are the corresponding to your favorite language. Then review the labels and descriptions and see if you can improve the existing or add a missing one. code) with the ?symbolHere is a query which lists all the coherent SI units, together with their unit symbol and the quantities which are expressed in this unit. Replace all instances of "en" (except next to
Use at
- https://query.wikidata.org/sparql
PREFIX wdt: <http://www.wikidata.org/prop/direct/>
PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX schema: <http://schema.org/>
PREFIX rdfs: <http://www.w3.org/2000/01/rdf-schema#>
select
?unit (sample(?label) as ?label) (sample(?desc) as ?desc)
(sample(?conversion) as ?conversion) (sample(?symbol) as ?symbol)
(group_concat(distinct ?quantity; separator = "; ") as ?quantities)
where {
?unit wdt:P31 / wdt:P279* wd:Q69197847 . # coherent SI unit
optional { ?unit rdfs:label ?label . filter (lang(?label) = "en") }
optional { ?unit schema:description ?desc . filter (lang(?desc) = "en") }
optional { ?unit wdt:P2370 ?conversion } # 1 for every coherent SI unit
optional { ?unit wdt:P5061 ?symbol . filter (lang(?symbol) = "en") }
optional { ?unit wdt:P111 / rdfs:label ?quantity . filter (lang(?quantity) = "en") }
} group by ?unit