When multiple intermediate solutions in a BGP resolve to the same
(s, p, o) triple-store query, only the first executes a round trip;
subsequent solutions replay cached results. This eliminates redundant
network calls in common patterns like type lookups where many entities
share the same rdf:type.

Measured ~70% reduction in round trips on a real query joining rdf:type
with rdfs:label (69 → ~9 queries).