Property paths — reachability without recursion

A property path lets one triple pattern match a route through the graph instead of a single edge. This is SPARQL's answer to recursive SQL CTEs — expressed in a few characters.

# Everyone reachable up an ancestor chain of any length:
SELECT ?descendant WHERE {
  ?descendant :ancestorOf+ :Splinter .
}

Where paths shine, and where they bite

• Reachability for free. :ancestorOf+, rdfs:subClassOf*, :partOf+ answer 'is X reachable from Y?' without materialised transitive triples or a reasoner.
• */+ find existence, not the path itself. A path query tells you that a route exists, not which nodes it passed through. If you need the intermediate steps, you need a different approach (enumerated hops or a graph engine).
• Unbounded */+ over a large graph can be expensive. Anchor at least one end with a constant (as above) so the engine doesn't explore the whole graph.

A property path is flight connections, not single flights. :flight matches one leg; :flight+ answers 'can I get from Zürich to anywhere, with any number of layovers?'. You learn whether you can arrive — the path operator doesn't hand you the boarding passes for each leg.