Ivan’s private site

I hit a small issue the other day, which was clarified by the DBpedia folks. I guess others may have, or will hit a similar issue; it may be worth therefore to document it.

The question I had: what URI should I use for J.S. Bach’s Well-Tempered Clavier? This is a non-trivial question if one wants to use, say, the Music Ontology in cataloging one’s music: indeed there is nothing like, say, ISBN-s in classical music. I am not sure who suggested in the past that using the corresponding Wikipedia URI might be the best option we have. Well, now that we have DBpedia, I thought that the corresponding DBpedia URI (the non-informational resource one, that is) should be a much better choice. But what is the URI?

I typed in “Well tempered clavier” in my Wikipedia search box, and this led directly to

http://en.wikipedia.org/wiki/Well_Tempered_Clavier

which displayed the corresponding article. Fine, so I thought by using a simple replacement, yielding

http://dbpedia.org/resource/Well_Tempered_Clavier

would give me the URI. Wrong, 404…

The issue (and that is where I was wrong) is that Wikipedia uses a funny, non-HTTP based redirection. It displays the right content for the search result, it keeps a kind of phony URI in the browser’s address bar, it just puts a small note into the article saying “(Redirected from XYZ)”. DBpedia does noe keep track of all possible search possibilities, so a URI minted from the redirected page (“redirected” in the Wikipedia sense) is not the right answer.

What to do? Here is what Richard Cyganiak proposed as a general approach:

1. Get your search term, have your article displayed
2. If the wikipedia in use is not the English one, click on the English link in the left sidebar (a Richard put it: if there is no English link, you are out of luck…
3. If the page is redirected (look for the note like the one I referred to), hit the “Article” button on the top of the page. This will redisplay the same article content, but with the “canonical” URI in the browser’s address bar.
4. Take that URI, and replace the leading http://en.wikipedia.org/wiki by http://dbpedia.org/resource

Voilà! You then get to

http://dbpedia.org/resource/Well-Tempered_Clavier

which can be used as a non-informational resource for this piece of music (note the difference in a hyphen in the URI!).

Thanks to Richard, Sören, and Georgi for enlightening me…

I must admit this news slipped my attention. I also have not seen it on, say, the blogs aggregated on PlanetRDF (which does not necessarily means it was not there, just that I was careless!). Anyway, it is worth repeating it: the OASIS OpenDocument Technical Committee approved its enhanced metadata support format [pdf] for inclusion in ODF 1.2. What this means for the Semantic Web community is that OpenDocument will rely on RDF for its metadata support. Meaning that, for example, information on documents in ODF 1.2 can be easily integrated with a bunch of other data. Yay!

Luckily, I read Bruce D’Argus’ blog this morning. Worth reading it, it contains much more information…

Chris Bizer has just published, on the home page of the “Linking Open Data” project, a new image showing the various interlinked databases:

Over one billion RDF triples, which are interlinked by 180,000 RDF links. Really impressive!

Unless you are a reporter, you rarely read press releases… however, the latest press release of OCLC is worth noting for the Semantic Web community: “OCLC to work with Zepheira to redesign OCLC’s PURL service”.

Two aspect of the announcement really caught my eyes:

1. The way I understand it, the service will provide an implementation of what became known as HttpRange-14, ie, how to define URI-s for informational and non-informational resources. And this is really great: indeed, the theory of HttpRange-14 is one thing, its practical deployment is another. Unless one has access to the controls of his/her server (eg,to an .htaccess file for an Apache server), it is not that easy to adopt it in practice. With the renewed PURL service this should become a breeze…
2. The code of PURL will be released as open source. Ie, other services can be set up using the same software and providing similar services. I could see a number of, say, specialized communities making use of that feature in future. I think this will play a very important role. (For example, look at the way UniProt defines its URI-s these days: the URI scheme used in the announcement, ie, http://purl.uniprot.org/{db}/{id}, suggesting that this community can very well make use of a renewed PURL software if they wish)

By the way, if you wonder who “Zepheira” is, look at their team page. Some familiar faces and names there…