Moving to New Zealand

Karen and I are taking the plunge together. Well, another plunge: we are emigrating to New Zealand at the end of this year.

This is not, of course, something you decide on a whim. We've both long felt that we might like to make a "big change" for the better, and a long holiday spent getting to know New Zealand and its people convinced us that it is everything we were hoping it would be. New Zealand is an absolutely breathtakingly beautiful place, its people are friendly and easy-going, and for what is basically a predominantly Anglosaxon culture they actually make very good coffee as well.

The plan is quite simple. We have both obtained our permanent residence visa, and will move to New Zealand, to the Wellington area, in December. Although neither of us has secured a job yet, I am actively on the lookout, and confident that something suitable will turn up. NZ and especially Wellington is full of smaller and larger IT firms, and every job vacancy site I check literally posts 2 to 6 positions for (Java) developers a day, at least. However, what I've not been able to find much of yet, is companies or institutes who work in Semantic Web/Ontologies, or who have a need for expertise in that area. If any of you have tips for me (or a job offer ;-)), it would be much appreciated!

I will post updates on developments now and then on this weblog. Oh and yes: we will of course be giving a farewell party later this year ;-)

wurvoc.org - linked open data for Quality of Life

I am proud to announce the official launch of wurvoc.org. Built by the Intelligent Systems Group at Wageningen UR Food & Biobased Research, the goal of wurvoc.org is to serve as a hub for various vocabularies and semantic web services we have developed and are still developing. Many of these vocabularies (modeled in RDF and OWL) have been built using public funding and we feel it important that this information is also publicly available in a way that is open and reusable.

Vocabularies

Currently, wurvoc.org publishes 4 vocabularies:

• The Ontology of Units of Measure models concepts and relations important to quantitative scientific research. It has a strong focus on units and quantities, measurements, and dimensions.
• The Food Additives vocabulary describes substances added to food to improve the flavour, taste, shelf-life, stability et cetera of the food product. Food additives that are approved by EFSA, the European Food Safety Authority are labelled with an E-number.
• The Dairy ontology contains a hierarchy of types of dairy products and provides general information about these products.
• The Drinks vocabulary contains a classification hierarchy of various types of beverages.

Our aim is both to publish more vocabularies and data in the near future, and to extend and improve the current vocabularies: although the data is Open, it is not yet truly Linked in the sense that it has very few relations with external datasets.

Software

We've developed the wurvoc publication platform, a set of REST services on top of the Sesame framework. In line with linked data principles, the platform publishes each vocabulary and each vocabulary term on its own URI. For example, an ontology on food additives is available at http://www.wurvoc.org/vocabularies/food-additives/, and the food additive Pectin is reprsented by http://www.wurvoc.org/vocabularies/food-additives/Pectin.

The platform uses HTTP content negotation to determine the representation format, currently supporting XHTML, RDF/XML, Turtle, N3, NTriples, and TriG (with JSON on the ToDo list).

OUM Web Services

Apart from a vocabulary publication platform, wurvoc.org also offers a number of SOAP-based web services on top of the Ontology of Units of Measure (OUM). These web services provide a number of useful functions, including lookup and matching functions as well as more advanced stuff, such as unit conversion or formulaic consistency checking.

Future plans

We are aiming to publish the publication platform software as open source as soon as possible. Various improvements are also planned, including a SPARQL endpoint and support for JSON.

I'd very much like to hear your comments on what we've brewed sofar, what you think is good and what you think could be better. I encourage you to reuse our linked data (and would appreciate it if you could let us know if you do).
I also plan to keep you up to date on our findings regarding use, performance, and general lessons that we learn after the launch of this project. Watch this space :)

Accessing DBpedia's SPARQL endpoint with Sesame

I'd like to share a tip on using Sesame as a client for SPARQL endpoints. This may be rather trivial to some but perhaps new to others.

We are developing a tool called ROC (Rapid Ontology Construction) (see our paper@ASWC'08), which is a tool that allows domain experts to quickly build a basic vocabulary for their domain, re-using existing terminology whenever possible. How this works is that the ROC tool asks the domain expert for a set of keywords that are 'core' terms of the domain, and then queries remote sources for concepts matching those terms. These are then presented to the user, who can select terms from the list, find relations to other terms, and expand the set of terms and relations, iteratively. The resulting vocabulary (or 'proto-ontology', basically a SKOS-like thesaurus) can be used as is, or can be used as input for a knowledge engineer to base a more comprehensive domain ontology on.

ROC is developed on top of Sesame, and up until now we simply supplied the tool with 'remote sources' by adding data to a locally running Sesame repository. In order to act with the LOD cloud, we obviously needed something a bit less awkward, so I started looking into ways to extend the functionality to be able to query linked open data.

Fortunately, I didn't have to look far, because Sesame actually already supports this: Sesame's client server protocol is a superset the SPARQL protocol. This I already knew, but what I hadn't yet tried was to see if that meant you could use Sesame's client libraries to query any SPARQL endpoint (instead of just connect to a remote Sesame server, which is what it is primarily designed for, after all). And guess what, it turns out that you can!

Here's a bit of code that connects to DBPedia's SPARQL endpoint and fires a query. The idea is simply to reuse Sesame HTTPRepository class, supply the endpoint URL as the server, and specify no repository:

String endpointURL = "http://dbpedia.org/sparql";
HTTPRepository dbpediaEndpoint = 
         new HTTPRepository(endpointURL, "");
dbpediaEndpoint.initialize();

RepositoryConnection conn = 
         dbpediaEndpoint.getConnection();
try {
  String sparqlQuery = 
         " SELECT * WHERE {?X ?P ?Y} LIMIT 10 ";
  TupleQuery query = conn.prepareTupleQuery(SPARQL, query);
  TupleQueryResult result = query.evaluate();

  while (result.hasNext()) {
      ... // do something linked and open
  }
}
finally {
  conn.close();
}

Now, I'm perhaps easily impressed, but to me this was beautifully easy. This makes integrating arbitrary linked open data in most of our Sesame-based tooling (including ROC) completely painless.