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).

My reading group presentation, entitled “An overview of RDB2RDF techniques and tools”, was be based on the RDB2RDF XG reports [2,3] and an overview of the performance of the reported tools [1].

The slides of the presentation can be found here.

Abstract (from [1]):
Many science archive centres publish very large volumes of image, simulation, and experiment data. In order to integrate and analyse the available data, scientists need to be able to (i) identify and locate all the data relevant to their work; (ii) understand the multiple heterogeneous data models in which the data is published; and (iii) interpret and process the data they retrieve. RDF has been shown to be a generally successful framework within which to perform such data integration work. It can be equally successful in the context of scientific data, if it is demonstrably practical to expose that data as RDF. In this paper we investigate the capabilities of RDF to enable the
integration of scientific data sources. Specifically, we discuss the suitability of sparql for expressing scientific queries, and the performance of several triple stores and RDB2RDF tools for executing queries over a moderately sized sample of a large astronomical data set. We found that more research and improvements are required into SPARQL and RDB2RDF tools to efficiently expose existing science archives for data integration.

[1] A. J. G. Gray, N. Gray, and I. Ounis. Can RDB2RDF Tools Feasibily Expose Large Science Archives for Data Integration? In L. Aroyo, P. Traverso, F. Ciravegna, P. Cimiano, T. Heath, E. Hyvönen, R. Mizoguchi, E. Oren, M. Sabou, and E. P. B. Simperl, editors, ESWC, volume 5554 of Lecture Notes in Computer Science, pages 491–505. Springer, 2009.
[2] A. Malhotra. W3C RDB2RDF Incubator Group Report. http://www.w3.org/2005/Incubator/rdb2rdf/XGR-rdb2rdf/, January 2009.
[3] S. S. Sahoo, W. Halb, S. Hellmann, K. Idehen, T. T. Jr, S. Auer, J. Sequeda, and A. Ezzat. A Survey of Current Approaches for Mapping of Relational Databases to RDF. W3C RDB2RDF XG Report, W3C, 2009.

Tomorrow will be 3 weeks since I got the iPhone 3Gs, so I thought I’ll write my first impressions.

So far some little stuff:

• No delivery report on SMS
• No sync with computer over bluetooth
• No dual dictionary (spelling for Portuguese and English) – this one is kind of solved: if you enable multiple language keyboards it will switch the dictionary according to the keyboard layout.
• I cannot find an option to get the iPod to do shuffle by albums, i.e., play one complete album and select the next one randomly. Or to sort the albums inside an artist by release date.

I like the keyboard, it’s easy to use (unlike I thought). And the overall use and integration between applications is very good. Not to mention the fact of being able to access the Internet anywhere!! Great stuff! I was thinking of getting a plan that did not include data access. This would be a big mistake since wouldn’t be able to use it to it’s full potential.

So now I’m trying the WordPress iPhone app that is available freely on the App Store.

Seems to be really nice and easy to use. Just enable remote posting in the blog, setup your user and password and you’re ready to go.

Let’s see how it looks

Of course typing on the iPhone is actually pretty good!

UPDATE: looks good, seems to be approved It’s possible to even add pictures which seems nice

Very pleased to announce that XSPARQL has been published as a W3C Member Submission!

Great reward for all the hard work from the our team. Congratulations to all.

Posting from an Acer Aspire One Ana got one for herself. Nice little “toy”.

The keyboard does take a bit of getting used to but after some time you can write at a good speed.. Other than that seems to do it’s job pretty well: Firefox runs smoothly, OpenOffice seems more than enough for the eventual text, Skype and MSN/Gtalk work without problems.

Runs a very nifty Linux Linpus Lite, based on Fedora.

Finally I started to build my webpage, the skeleton is in place, just need to include more information.

Also changed the theme of this blog to be a bit more similar to the webpage.

Is there such a thing as too much music? If so, when do you know you have saved too much music?

A while back I decided to listen to all my music once. I now checked when I started and, according to last.fm, it was last September. I’m only though to letter ‘D’. Maybe I just don’t listen to enough music because I know I’m by far not to have a lot of music.

What’s the point in using up disk space to store music you have no time to listen to?!?

Lifehacker posted some time ago some tips on how to make iTunes more bearable. Still far from perfect