DVD Burners
Tonight will be relatively short. Why? Because I've just spent hours trying to get my DVD burner to burn! I spent quite a few hours on the weekend as well.

I regularly update Debian, so it's always possible that I got a new version of a library or something, so when a backup didn't work for me yesterday I spent many hours trying different methods of writing to a disk. I had another go today, and I've been getting more and more frustrated as time went past.

The drive is an LG GSA-4081B. This is a nifty drive that burns DVD+-R(W) and DVD-RAM. The DVD-RAM has been particularly nice, and I've used it often. However, I had quite a bit of unchanging data that I wanted to back up, so I popped in a DVD-R, only to discover that it won't work for me. I have DVD-R discs I've burned with it in the past, so I know it used to work. I've used every driver available for dvdrecord and cdrecord-ProDVD, and on each occasion it tells me that the drive is not ready. I went out and found the latest firmware, to no avail... though it did fix an ongoing issue I've had reading data from the second layer of a DVD in Linux.

Finally I tried doing a mke2fs on a DVD-RAM disc, and that failed as well. Since I use these discs all the time I realised that I now had a real problem. Strangely, it still writes to already formatted discs, so the burning laser is operational. In the end I gave up, and did what I should have tried hours ago... I ran Windows.

Once in Windows I started running the software that came with the drive. It all seemed easy enough, but when it asked for me to insert a disc it wouldn't recognise when one was there. After several ejections and re-insertions of a DVD-R it finally acknowledged a disc, but then immediately came up with an error. I tried the same thing with a DVD-RW disc with the same result.

So now I've found the receipt and I'll be calling UMart in the morning. I hate trying to convince suppliers that I have intermittently faulty equipment.

At least my PowerBook is now in the country. Hopefully I'll see it in a few days. Apple can be a little slow about these orders though, so I'd better not hold my breath.

Rules Engines
I spent most of today reading documentation for Mandarax and Drools. "Silly me" went and started learning the architecture rather than the API before I realised exactly what Drools is. This was definitely not needed for what we plan on doing with it, since Drools is really just a framework for executing rules as needed. Perfect for RDFS. On the other hand, it was useful reading a description of the RETE algorithm.

I haven't really got into Mandarax yet, as I won't be using it to start with. However, it has some great potential for providing backward chaining. For on-the-fly inferencing this will be essential, but it seems that there are no commercial applications out there that do this. Obviously backward chaining is not an easy thing to address, but it is still an important thing for us to get working.

Anyway, I have a little more to learn about Drools tomorrow, and then I'll be attempting to set up some simple rule systems just to make sure I have my head around it. With any luck I'll have the RDFS rules going in a couple of days.