query-b3a1a5d4a454a9f3a53042549d509218
Quantities: Instances and Classes, similar, large scale improvements will be possible. However, one issue in Wikidata is the classification of (physical) quantities: What are the individuals and what are the classes? I estimate that Wikidata has items for about 1000 physical quantities, but currently there is no single query that finds all of them, and nothing more. (P7431)Wolfram Language quantity ID , which allows for instance comparison of conversion factors. Now that we have (P7007)Wolfram Language unit code In recent weeks I've been improving units in Wikidata, which is still a large, ongoing and probably never ending project. Very helpful was alignment with the WL by the property . (Q568496)ISO/IEC 80000 and (Q70257574)International Vocabulary of Metrology (3rd edition, 2012) . It is consistent with the treatment of quantities in the relevant standards, namely (Q71548419)Defining 'kind of quantity' I'd like to propose following the scheme outlined in Proposal (using examples; for precise terminology, refer to the text): 5 kg is an "instance of" mass; 5 kg is also an "instance of" a physical quantity radius is a "subclass of" length; lengths is a "subclass of" physical quantity length, area, radius, apple count, ... are classes of individual quantities 5 kg, 3 apples, 5 rad, ... are individual quantities: Page 5, figure 2 illustrates this idea very nicely. The box called M0 are what Wikidata calls "instances". The box called M1 contains classes, solid arrows are "subclass of" relations in Wikidata. (Q71548419)Defining 'kind of quantity' Notes on If we consistently follow that scheme then query [1] will contain exactly those elements that we have in mind when talking about "physical quantity". I'm writing this comment to raise awareness of the tricky issue "instance of" vs "subclass of" in the context of quantities, to solicit feedback, support or criticism, and potentially pointers to previous discussion that I have missed. [1] Query physical quantities (the classes like "length", "area", not the individuals like 5 m, ...):
Use at
- https://query.wikidata.org/sparql
PREFIX wikibase: <http://wikiba.se/ontology#>
PREFIX wdt: <http://www.wikidata.org/prop/direct/>
PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX bd: <http://www.bigdata.com/rdf#>
select distinct ?pq ?pqLabel where {
?pq wdt:P279* wd:Q107715 . # physical quantity
service wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en" . }
}