- From: Toby Inkster <tai@g5n.co.uk>
- Date: Wed, 20 Jan 2010 06:37:22 +0000
- To: Steve Harris <steve.harris@garlik.com>
- Cc: Danny Ayers <danny.ayers@gmail.com>, jeremy@topquadrant.com, "semantic-web@w3.org" <semantic-web@w3.org>
On Fri, 2010-01-15 at 22:06 +0000, Steve Harris wrote:
> There is a cost to opening up what can go where in triples. My SPARQL
> engines (and I expect those of others) use this as a source of
> optimisations. E.g. if some variable appears in the predicate slot,
> then you know it can only bind to a URI, and you can limit your search
> space.
I seem to remember that in Virtuoso TP1, the following query:
SELECT *
WHERE {
?s ?p ?o .
OPTIONAL { ?o ?q ?v . }
}
"optimised" things by making the assumption that ?o was not a literal.
:-(
--
Toby A Inkster
<mailto:mail@tobyinkster.co.uk>
<http://tobyinkster.co.uk>
Received on Wednesday, 20 January 2010 06:38:13 UTC