Today our diploma student Christian Weiske finished the last bits of his RAP based database-driven SPARQL engine which implements most parts of the W3C recommendation now. Compared to the current memory-based SPARQL engine in RAP, SparqlEngineDb generates SQL queries to load off the hard work to the database engine. This speeds up SPARQL queries greatly, allowing operation on millions of RDF statements with ease, and without worrying about PHP memory consumption.
A new version of RAP including the new engine will be released shortly. In the meantime, Powl and OntoWiki internals will be switched to use SPARQL queries making it possible to use different data backends.