- From: Axel Polleres <axel.polleres@urjc.es>
- Date: Sun, 03 Dec 2006 03:21:03 +0100
- To: public-rdf-dawg-comments@w3.org, public-rdf-dawg@w3.org
Dear members of the DAWG, Over the last few months I did some investigation on the relations between SPARQL and rules languages, more precisely between SPARQL and Datalog. The results are written down in the following technical report which I hope contains some useful insights and which I also plan to send to the SPARQL working group: http://www.polleres.net/publications/GIA-TR-2006-11-28.pdf You find the following in there: * I refine and extend the recent proposal to formalize the semantics of SPARQL from Pérez et al., presenting three variants, namely c-joining, s-joining and b-joining semantics. * Based on these three semantic variants, I provide translations from a large fragment of SPARQL queries to Datalog, which gives rise to implementations of SPARQL on top of existing rules engines, a prototype is available at http://con.fusion.at/dlvhex/download.php * I'd like to suggest to the working group some straightforward extensions of SPARQL such as adding the set difference operator MINUS, and allowing nesting of ASK queries in FILTER expressions which come basically for free in the approach. * Finally, I discuss an extension towards recursion by allowing bNode-free-CONSTRUCT queries as part of the query dataset, which may be viewed as a light-weight, recursive rule language on top of of RDF. My background is that in the RIF working group we discussed a while ago how/whether to cover SPARQL queries in rule bodies there, which drew my interest to the topic. I hope that sharing my insights with you this way is also useful for the DAWG work. Looking forward to comments/discussions! best regards, Axel -- Dr. Axel Polleres email: axel@polleres.net url: http://www.polleres.net/
Received on Sunday, 3 December 2006 02:32:39 UTC