human
Group buildings by construction year and show the average number of units in each year group.
gpt
```sparql
PREFIX :       <http://example.org/ontology#>
PREFIX rdf:    <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT ?year (AVG(?units) AS ?avgUnits)
WHERE {
  ?b rdf:type :Building ;
     :hasNumberOfUnits ?units ;
     :hasConstructionYear ?year .
}
GROUP BY ?year
```