Wikidata:WikiProject Ontology/Problems/High order metaclasses

Problems with higher order metaclasses

A class can be identified as such by itself being a subclass of another class, by having another class be its subclass, or most directly by having instances. These provides three different mechanisms for detecting higher order classes as well, as the following queries illustrate.

• Wikidata:WikiProject Ontology/Problems/3rd order metaclasses by subclass
• Wikidata:WikiProject Ontology/Problems/3rd order metaclasses by superclass
• Wikidata:WikiProject Ontology/Problems/3rd order metaclasses by instance

These are only looking at direct instance-of relationships up the hierarchy. The most general query along these lines would look like, for example:

select DISTINCT ?item WHERE
  { ?metametaclass wdt:P31 ?item .
    ?metaclass wdt:P31/wdt:P279* ?metametaclass .
    ?class wdt:P31/wdt:P279* ?metaclass .
    ?otherclass wdt:P279 ?class . }

Try it!

However this times out in WDQS.

'concept'

concept (Q151885) comes up as a high-level metaclass in many subclass of/instance of trees; for example:

• champagne (Q134862) instance of wine (Q282) subclass of ... liquid (Q11435) instance of fundamental state of matter (Q15831576) subclass of ... state (Q3505845) instance of concept (Q151885)

but concept then has two more levels above it that cross the instance-of (metaclass) leap:

• concept (Q151885) subclass of mental representation (Q2145290) instance of symbol (Q80071) subclass of ... depicting object (Q1166770) instance of physical object (Q223557)

symbol (Q80071) itself also appears frequently near the top of the ontology trees. This should probably be cleaned up.