human
List the building and year, but only if year is known.
gpt
```sparql
PREFIX :    <http://example.org/ontology#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT ?building ?year
WHERE {
  ?building rdf:type :Building ;
            :hasConstructionYear ?year .
}
```