Open world assumption and SPARQL in triple stores

Question

I would like to know if SPARQL, by default, adopts the open world assumption or if this depends on the triple stores that execute the SPARQL queries.

And what are th

Answer 1

Well....

I wonder whether this is really a good question for this site. I think not, but I'm gonna throw a few cents into the bucket anyway.

To start with -- does it matter whether SPARQL "adopts" (and what does that mean, to you?) OWA, and, if so, why?

Then, to address @AKSW's comment -- W3 differs with @AKSW's assertion, in at least the RDF 1.0 Spec (granted, that has since been revised to RDF 1.1, and the key statement has now been left out; regrettably, "What's new in RDF 1.1" doesn't mention this omission), and a draft of the Government Linked Data WG Glossary (again, later omitted without explanation I could find). Wikipedia and various others concur, that RDF does base itself on OWA.

OWA basically says, if I don't have a statement (or its inverse) explicitly providing its truth or falsity, the answer to "is this statement true?" is neither "yes" nor "no," but "I don't know."

In similarly overly-simplified terms, SPARQL looks in a given Graph for matches to a Basic Graph Pattern. If the match is not found, the answer is not TRUE ... but does this mean that the pattern is therefore FALSE? I suggest, no.

But again -- so what? What's your use case? Are you working with sparse data, or solid data? Far too much of your question is left open; still, it's easy to answer based on a closed world assumption...

Answer 2

SPARQL follows the Closed World Assumption and assumes RDF data to be complete. This does not affect positive queries, but SPARQL queries with negation make only sense under closed world semantics.