Change 553757 had a related patch set uploaded (by DCausse; owner: DCausse):
[wikidata/query/rdf@master] Increase the max allowed query timeout

https://gerrit.wikimedia.org/r/553757

select ?p (count(*)as ?cnt) {
  ?s ?p ?o .
  filter ((!isLiteral(?o))&&(!isUri(?o)))
}
group by ?p

This can be simplified using isBlank, I believe:

SELECT ?p (COUNT(*) AS ?cnt) WHERE {
  ?s ?p ?o.
  FILTER(isBlank(?o))
}
GROUP BY ?p

But in general, are these triples interesting in wdqs? Since they're never used as subject there are no way to use them directly, it seems the only thing that we can do is to display them (T173248).

I’m not sure what you mean, to be honest… but they’re used in some useful queries, e. g. heads of state and government (“end time” qualifier absent or unknown) or anonymous paintings (unknown creator). You can find more by searching for isBlank on Wikidata project pages (most results use !isBlank to filter out blank nodes, but there are some non-negated uses too).

Blanks are used as representation of "unknown value" in Wikibase. Also, they are used (completely unrelatedly) in implementation of OWL class that describes "no value" properties (as "no value" is not a value, it is implemented with a predicate and a class instead of usual property predicate).
The class definition itself is useful only for the tools that actually understand OWL semantics. Most tools that query WDQS do not.

In T239414#5702018, @Lucas_Werkmeister_WMDE wrote:

But in general, are these triples interesting in wdqs? Since they're never used as subject there are no way to use them directly, it seems the only thing that we can do is to display them (T173248).

I’m not sure what you mean, to be honest… but they’re used in some useful queries, e. g. heads of state and government (“end time” qualifier absent or unknown) or anonymous paintings (unknown creator). You can find more by searching for isBlank on Wikidata project pages (most results use !isBlank to filter out blank nodes, but there are some non-negated uses too).

Thanks for the links, I was not aware of these usecases. As to what I meant when saying that these triples are not interesting, I did not think that they could be used as filters like that, what I understand about blank nodes is that they are useful to link triples using a resource that cannot be named. In this case they do not link anything and we seem to just use the fact that they are "blank" to determine/filter something. Perhaps an approach similar to wdno would have worked here? Anyways, this is certainly not worthwhile reconsidering this at this point and I'm certainly lacking a lot of context as to why such decisions were made.

Also I realize that this ticket is lacking some context, I will amend it to mention the reasons why we are investigating bnodes.

Change 553757 merged by jenkins-bot:
[wikidata/query/rdf@master] Increase the max allowed query timeout

https://gerrit.wikimedia.org/r/553757

We need statistics on how many triples use bnode as an object:
{code}
select ?p (count(*)as ?cnt) {

?s ?p ?o .
filter (isBlank(?o))

}
group by ?p
{code}
and as a subject (if any)
{code}
select ?p (count(*)as ?cnt) {

?s ?p ?o .
filter (isBlank(?s))

}
group by ?p
{code}

P9859 contains the output of

select ?p (count(*)as ?cnt) {
  ?s ?p ?o .
  filter (isBlank(?o))
}
group by ?p

ran on wdqs2006

Will run the same query but with a filter on the subject as asked, expectations here are to find only owl:complementOf around 42K.

select ?p (count(*)as ?cnt) {
  ?s ?p ?o .
  filter (isBlank(?s))
}
group by ?p

output is at P9862

and as expected we only see the corresponding subjects of the owl constraint on owl:complementOf (rdf:type, owl:onProperty and owl:someValuesFrom) as exported by the wikibase today:

wdno:P31 a owl:Class ;
	owl:complementOf _:genid1 .

_:genid1 a owl:Restriction ;
	owl:onProperty wdt:P31 ;
	owl:someValuesFrom owl:Thing .

@Igorkim78 could you take a look?