-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi Rob,
On 29/01/13 18:11, Rob Walpole wrote: > Am I doing something wrong here? The short answer is that the inner SELECT is evaluated first, leading to the results being calculated in the second case in a rather inefficient way. In the first inner SELECT ?deselected is bound, so it's quite quick to find all its ancestors. In the second, all possible ?deselected and ?ancestor pairs are returned by the inner query, which are then (effectively) filtered to remove all the pairs where ?deselected isn't whatever it was BINDed to. Here's more from the spec: <http://www.w3.org/TR/sparql11-query/#subqueries>. I /think/ ARQ is able to perform some optimisations along these lines, but obviously not for your query. Best regards, Alex PS. You don't need to do URI("http://?";); you can do a straight IRI literal: <http://?> - -- Alexander Dutton Developer, Office of the CIO; data.ox.ac.uk, OxPoints IT Services, University of Oxford -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.13 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJRCBMZAAoJEPotabD1ANF7Fb0H/jeCedjfCIuhI2KTNETOcrVR Gvl8N4k9ty4AN4F0xFKA3kcGCTR2CIpgz/hez6BM5s8mDqLc7ViNPXWxbUhb4kHh fxVuuoYBr13VhGnyufvWFliFeT3xSVLO3eDUilzoja2pvH/Cx/sNQvcHbi2Ee+EX MoWLyfSvtSGY2rXDmMAXvBz49wgk42mC2Bsr5ptNUfXWQjzz6BXp5SxTKADySBXG Tm/DmqGRclHxw233I6EcB9lKfDytTosVugH1Yl0BGEHiFPL2/wkkB+AZiLIwCmb/ cy+Y8/I9PlD4onvYlDMRmP169HQVYt849Skx5/TnTyjMBBNIgQiE8+cj0a/oDc8= =ZQec -----END PGP SIGNATURE-----
