Ontopia 5.0.0 enabled a new tolog optimizer by default, a move we knew risked causing difficulties for customers. One customer (NRK/Skole) has reported that they suspect this change caused problems for their application following the upgrade.

It is possible to control which optimizers are turned on and off in queries by including a comment in a special syntax. Unfortunately, in order for NRK to turn off the new optimizer in their application, they need to add that OPTION string to every single query in their application, since in 5.0.0 there is no way to set the option globally.

To avoid this, revision 450 implements a file called This is a normal Java properties file, loaded from the classpath. In the new version, options in the query take precedence over options in, which again take precedence over the defaults.

This means you can now control properties globally for your application, should you wish to. If there is no everything will work as before.

Computer Society meeting notes

The Computer Society meeting about Ontopia on Tuesday was quite well attended, and had quite a bit of discussion about both the use cases and the Ontopia project in general.

The first presentation was by Lars Marius Garshol about the City of Bergen project. The slides are not posted, since they were just a shortened version of the original talk, which was also published in the TMRA 2007 proceedings.

The second presentation was about the same project, but given by Ragnar Bøe of the City of Bergen administration. Slides here (warning: Norwegian).

The third presentation was a joint presentation by Geir Ove Grønmo (of Bouvet) and Per Magnus Løvold (from the customer) about the NRK/Skole project for Norwegian National Broadcasting. Slides in Norwegian.

The final presentation was a presentation of the status of the Ontopia project two months into the project by Lars Marius Garshol. The slides are in English.

Afterwards some of the attendees moved on to beers at Myrens Verksted, as usual.

Ontopia on Google AppEngine

Google AppEngine
Google AppEngine

Stig Lau has set up an example Ontopia application (source) running on Google AppEngine. This means that Ontopia web applications can run on Google AppEngine, which again means that it’s possible to get free hosting (up to a certain limit) for Ontopia-based web applications.

Note that there are some limitations. Firstly, this does not apply to the 5.0.0 release; Google AppEngine only works as of revision 421. Secondly, it only works with the in-memory backend for now. We are considering to try running with a pure-Java database to see if that is possible, in which case this could become a very interesting option indeed.

A Maven repository for Ontopia

Developers using the Maven build tool (or Ivy) can now get Ontopia from the Maven repository which Stig Lau just set up for Ontopia. This means that instead of having to download Ontopia and put it on the classpath they can instead just refer to the repository, and Ontopia will be automatically downloaded from there.

In the longer term, the aim is to get Ontopia into some other Maven repository, so that users do not have to reference a special repository just to get Ontopia. We are still working on this.