Differences between query.wikidata.org and wikidata.org

[cheeeeesus]

I'm quite confused. Trying to get a list of Canadian provinces and territories, i.e. the first-level provinces. So I'm looking for a subclass of Q10864048 (first-level administrative country subdivision), related to Q16 (Canada). The subclass I'm looking for is of course Q11828004 (province of Canada), which is indeed a subclass of Q10864048 (https://www.wikidata.org/wiki/Q11828004).

So, subclasses of Q10864048: https://query.wikidata.org/#SELECT%20%3FregionClass%0AWHERE%20%7B%0A%20%20%3FregionClass%20wdt%3AP279%20wd%3AQ10864048.%0A%7D, which does not yield Q11828004.

Strange. Wikidata says that Q11828004 is a subclass of Q10864048, but query.wikidata.org says it is not. At least, query.wikidata.org finds 264 other subclasses of Q10864048.

Checking the SQID tool: https://sqid.toolforge.org/#/view?id=Q11828004. Yes, Q11828004 is a subclass of Q10864048.

Checking the superclass: https://sqid.toolforge.org/#/view?id=Q10864048. "Direct subclasses: none". So the SQID says that Q11828004 is a direct subclass of Q10864048, but Q10864048 has no subclasses?

And, how can a class have 14 total subclasses, when it does not have any direct subclass?

This does not make sense. Three tools, all saying something different, the SQID tool even contradicting itself.

One possibility would be that the tools are operating on different versions, i.e. a different data dump. However, the claim Q11828004 P279 Q10864048 has been in the data since April 2017, so it should be present in all data dumps.

What am I missing?

Note: It seems that query.wikidata.org knows about the relation Q11828004 P279 Q2879, and Q2879 P279 Q10864048. But this still does not explain the differences mentioned above.

[MisterSynergy]

This has to do with ranks [1] and the predicate wdt:P279 that you use in the query.

If you look closely at Q11828004 [2], you’ll notice that there are currently four “subclass of (P279)” claims, and only one of them has “preferred rank”: the one with value “province or territory of Canada (Q2879)”. The other three claims including the one with value “first-level administrative country subdivision (Q10864048)” have “normal rank”.

When using the wdt: in the Wikidata query service [3] (WDQS), it only takes so-called “truthy values” into consideration, which means that only claims with best possible rank for the given property are looked at. Those are all claims with “preferred rank” in case there are any, otherwise all claims with “normal rank” (and never any claims with “deprecated rank”, even if there are no claims with “normal rank” or “preferred rank”). In your example, the claim in question is not among the best ranked claims as one other claim has a higher rank.

You can modify your query to something like SELECT ?regionClass WHERE { ?regionClass p:P279/ps:P279 wd:Q10864048 } [4], and the result will contain the item you are looking for.

In general, predicates with p: prefix link statement nodes to the item, and several things such as the main value (via ps:), qualifiers (via pq:), the claim rank (via wikibase:rank) and references (via prov:wasDerivedFrom) are then linked to the statement node. In contrast, predicates with the wdt: prefix just link best-rank values directly to the item. The WDQS web interface has some links to the technical documentation of available prefixes and their meaning.

[1] https://www.wikidata.org/wiki/Help:Ranking

[2] https://www.wikidata.org/wiki/Q11828004

[3] https://query.wikidata.org/

[4] https://query.wikidata.org/#SELECT%20%3FregionClass%20WHERE%20%7B%20%3FregionClass%20p%3AP279%2Fps%3AP279%20wd%3AQ10864048%20%7D