- From: Andreas Langegger <andreas.langegger@gmx.at>
- Date: Thu, 26 Apr 2007 23:06:55 +0200
- To: semantic-web@w3.org
Hi Paul, thanks for the hint. I know Mulgara and I've also read about these issues with Kowari and Tucana. However, at first I was looking for a SPARQL-implementation since we wanted to be as close as possible to evolving standards. I will take a closer look on Mulgara again. We need support for aggregate functions and would have to extend SPARQL anyway. Are there agg functions except count, like sum/min/max/avg...? And we also need iterators resp. cursors for SPARQL results. Are there any publications about query processing/optimizing in Mulgara? Does anybody now about clustered Kowari/Mulgara application scenarios. We are working on a distributed query processor for SPARQL. Any pointers are appreciated. Thanks again and best regards, Andy Paul Gearon schrieb: > Hi Andy, > > While not network or hierarchical, the Mulgara database > (http://mulgara.org/) was written from the ground up to take RDF data > and nothing else. The database used to be called Kowari, and before > that it was a commercial system called TKS (Tucana Knowledge Store). > > To describe it briefly.... > > Mulgara does OK on 32 bit systems, but it scales really well on 64 bit > systems. All joins are evaluated lazily, which removes memory limits, > and complex queries don't cause any problems. We have been slow getting > SPARQL supported (though some simple SPARQL queries already work) but we > support our own query language that predates SPARQL by several years and > offers several more features. These features include extra join > operations, and insert/delete commands. There is also an SPI for > plugging any kind of external data source in as a supplemental back-end. > > We went through a quiet period after the company that started the > original project shut down, but the project has been actively moving > ahead for the past year, with a few new features and a lot of bug fixes. > > > Regards, > Paul Gearon > > On Apr 25, 2007, at 4:30 AM, Andreas Langegger wrote: > >> >> -----BEGIN PGP SIGNED MESSAGE----- >> Hash: SHA1 >> >> Dear group members, >> >> most of currently available RDF triple store implementations (Jena, >> 3store, sesame, etc.) use relational database systems as the underlying >> information system. Well, I guess this is because they are well known, >> have proven to scale and perform, you get existing features for data >> management, indexing, transactions, etc. and can use existing tools. >> >> However, are there any resources (papers/projects/links/...) where RDF >> storage in network/hierarchical databases is investigated? Would there >> be benefits? >> >> The bottlenecks with RDBMS are either huge joins over the same table => >> memory problem for large datasets or complex query processing which at >> the moment has to be done in the higher app level. There should be >> better support inside the DBMS in future like special join operations. >> >> If sb has pointers or comments, I'd appreciate! >> >> best regards, >> Andy >> >> - -- >> - ---------------------------------------------------------------------- >> Dipl.-Ing.(FH) Andreas Langegger >> Institute for Applied Knowledge Processing >> Johannes Kepler University Linz >> A-4040 Linz, Altenberger Straße 69 >>> http://www.faw.at >>> http://www.langegger.at >> -----BEGIN PGP SIGNATURE----- >> Version: GnuPG v1.4.2.2 (GNU/Linux) >> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org >> >> iD8DBQFGLx+oKk9SuaNc5+IRAhuRAKDVaCd+Gur+rWZlRH6ZC2HbePBVCgCg2iJ5 >> eGHDozDvl7EauBy06TFnsZ8= >> =H1Ia >> -----END PGP SIGNATURE----- >>
Received on Thursday, 26 April 2007 21:07:10 UTC