nl’s weblog

The W3C has just announced the launch of the RDB2RDF Working Group (WG). Three researchers from DERI will join this WG: Michael Hausenblas (one of the co-chairs), Richard Cyganiak and myself.

As stated:

The mission of the RDB2RDF Working Group, part of the Semantic Web Activity, is to standardize a language for mapping relational data and relational database schemas into RDF and OWL, tentatively called the RDB2RDF Mapping Language, R2RML.

One of the more important aims of this mapping language is to easily expose data in your relational database as RDF. You can check my presentation about this topic for a DERI reading group.

This is related to my research topic (which needs to be further refined in the following months) since we want to add relational databases as a source of data to our XSPARQL framework.

Last week (30/08 – 04/09) was held the 2009 (5th) edition of the Reasoning Web Summer School in Brixen-Bressanone, Italy, hosted by the Free University of Bolzen-Bolzano.

This year all the talks were very interesting. Bellow is a short overview of them, presenting the main topics covered:

• Description Logics by Franz Baader

In this tutorial we had a good introduction to Description Logic (DL) presenting the ALC description language along with the necessary definitions. This gave the background to present reasoning in DLs, namely Tabelaux and Automata based approaches. The final part of the tutorial was about reasoning in the “light-weight” DLs EL and FL₀.

• Answer Set Programming: A Primer by Thomas Eiter, Giovambattista Ianni, Thomas Krennwallner

This tutorial consisted of 3 different parts: firstly Thomas Eiter presented all the formalisms and theory behind the Answer Set Programming (ASP) declarative programming paradigm and several extensions such as strong negation and disjunction. Thomas Krennwallner followed by presenting some common methodologies for problem solving using ASP and finally Giovambattista Ianni presented the Semantic Web related extensions of the DLV system.

• Logical foundations of XML and XQuery by Maarten Marx

Maarten Marx presented a good introduction to XPath, making the connection to it’s logic roots. A more detailed look into some of the XPath functions was provided, showing practical use-cases for these.

• Foundations of RDF Databases by Claudio Gutierrez, Marcelo Arenas, Jorge Perez

This tutorial, fully presented by Marcelo Arenas, focused on RDF datamodel and RDFS inference rules, complexity and optimization of SPARQL query answering. Also presented was they’re approach for querying RDFS with SPARQL: a navigational language (with similar aspects as XPath) for SPARQL called nSPARQL.

• Database Technologies for RDF by Souripriya Das

The lecturer, from Oracle, presented several key concepts on database representations and optimizations for RDF storing with querying in mind. The representation needs to allow for effective storage and querying. Also presented the language they’re using for RDF querying, which consists of SQL allowing graph patterns in the WHERE clause. Interesting since it allows to reuse all the well established SQL features.

• Technologies for the Social Semantic Desktop by Siegfried Handschuh, Michael Sintek

Siegfried Handschuh presented an overview of the challenges of building the Semantic Desktop. Started a bit of history (Vannevar Bush, Doug Englebart) and with a very high level description of the vision and proceeded to a more in-depth presentation of Nepomuk, Semanta and the Nepomuk Representational Language.

• Ontologies and Databases by Diego Calvanese

This lecture presented the techniques of reasoning and query answering for DLs (Lite), such as query reformulation (based on the TBox) and taking into account certain assumptions held for relational databases (for instance, unique name).