Monday, November 29, 2004

With TJ back we spent a little time talking about the needs of the customers he spent the week with. Most of it seems to come back to the work we are currently doing, but I think it has focused TJ's ideas a little.

We had a chat this afternoon about the OWL resolver he would like to see. I was initially worried about this, but in the end I've been mollified. Basically, it will return statements from a model of inferenced data, combined with the model of base facts. The techniques I'm using to create an inferred model will be essentially the same, but now there will be some extra information on how the models relate. This will allow many operations occur automatically whenever the OWL resolver is used. I'm all for this approach, so I'm happy to go ahead with it.

In the meantime TJ is very keen on the idea of the "change problem", which I've been avoiding up until now. While I know how essential it is, I think I've talked him into letting us get inferencing working correctly first. I think this is important, as we need to learn to walk before we can run. While I've done no work and little research on the problem so far, I have been thinking about it, and I can think of several things we can do to make this work more efficiently than the brute-force approach. However, I also think that we will learn some lessons as we implement the brute-force method. So I believe that putting off this design for the time being will allow us to get a working (though slowly updating) system in a shorter timeframe, and allow the final version to be better designed and faster than if we attempted it from the outset.

Looping Bug
I was back onto this after a weekend away from it all.

An initial discussion with AN revealed that the JRDF and Jena code actually use the LocalSessionFactory class, and not RMI (yay, I was beginning to lose faith). This ran counter to SR's earlier assertion that the code which returned a LocalSessionFactory was no longer in use. AN seemed initially skeptical that no one else used anything but RMI, but I eventually convinced him.

So this left me in a position of trying to create a LocalSessionFactory and returning it from the findSessionFactory() method when the NonRemoteSessionException method is thrown from the RmiSessionFactory constructor. Writing the code for this was the easy part. Getting it to work in the tests was the difficult part.

Unfortunately, no one seemed to have access to the LocalSessionFactory class. I spent more than a little time looking through the myriad build scripts trying to find where I should add it, but with little luck. On each occasion when I thought I'd found it, I added the needed classes to the appropriate jar and re-ran the tests. On each occasion I discovered that I hadn't found the correct place.

I really beat my head against a brick wall on this today, with little progress. Only as I was leaving did I think to look for the jar file which implements RemoteSessionFactory as this must also have access to the local data store. I thought I might get to it tonight, but I've spent quite a bit of time catching up on last week's blog, so I'll be doing it in the morning instead.

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