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Finding classes which should be instances sparql; Finding classes with exactly 1 subclass
发布于 2021-02-01 15:13:00
It sounds quite simple but I have not managed to find a nice solution yet. I'm looking to find the classes in my ontology which have exactly one subclass.
So far I have approached it as follows:
SELECT (COUNT(?anything) AS ?count) ?class
WHERE {
GRAPH <> {
?class rdf:type owl:Class.
?class rdfs:subClassOf ?anything.
?anything rdf:type owl:Class.
} group by ?class
I should then theoretically be able to sort on count, and the results that have value 1 should have only have 1 subclass. However, when I execute this query, the counts do not correspond with what I expect at all e.g. my test case should return 1, which it does, but another class which doesn't have a subclass at all, also returns 1. And a class with 3 subclasses returns a count of 4.
in the image below, it should find that the highlighted classes have a count of 1.
Questioner
Robin
Viewed
11
Thank you both! This helped immensly. I have now learned about "Having". I also did not know a class could be a subclass of itsself, so the filters are helpful.
Perhaps more telling and frustrating to me, the real problem was my declaration in the WHERE statement, if I had flipped this statement: ?class rdfs:subClassOf ?anything. I would have already gotten correct answers in my case, but it's good to know that this might not always be correct, hence the filters.
@robin yes, a class X is a sub class of Y when everything that has type X also has type Y. So, every class is a subclass of itself. Typically we won't assert that directly, but an OWL reasoner will recognize it.