human
Find the earliest construction year among buildings and roads together.
gpt
```sparql
PREFIX :    <http://example.org/ontology#>
PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>

SELECT (MIN(?year) AS ?earliest)
WHERE {
  {
    ?x rdf:type :Building ;
       :hasConstructionYear ?year .
  } UNION {
    ?x rdf:type :Road ;
       :hasConstructionYear ?year .
  }
}
```