Thoughts and Ramblings

I started to suspect that this was my fault, since this one podcast, Escape Pod was a podcast I was listening by going through its archives. I had written a program which downloads the archived episodes, and modifies the ID3 tags so iTunes will properly recognize the file as a podcast and insert it into its database as if it had downloaded it itself. Getting the release date working correctly was one of the harder points, so I figured that I still didn’t have it quite correct and the new iPod firmware was being more sensitive to it. I got even more annoyed by the fact that iTunes, after upgrading my iPod’s firmware, decided to trash the old firmware versions preventing me from ever downgrading.

Well, after much hassle, I now have a new car. Here are some pictures:

The whole ordeal was mostly due to the CARS program, which is often known by “Cash for Clunkers”. Anyway, I finally got that resolved and got a lot more for my old truck than I would have ever gotten in trade-in value. So now I have a VW Jetta, and so far I’m happy with it. I just need to get used to driving a car instead of a truck, but otherwise it drives well.

I use MacPorts to get a whole host of utilities. In addition, I’ve always used it to obtain later versions of subversion that the one provided with the OS. Xcode, on the other hand, is locked into using the version of Subversion which is installed in /usr (currently version 1.4.4 where as I have 1.6.3). Since I often work in the command line, eventually I will use the newer version of Subversion on a directory which I also use in Xcode. This causes a problem since the command line utility will upgrade the local repository format in such a way that old versions of Subversion (Xcode’s) cannot use it.

When I redesigned Sapphire, I decided that the metadata back end would be best served by Apple’s Core Data Framework. While the framework has a lot of power, several shortcomings in the implementation hindered its potential.

First, I should start with the many things that Apple did correctly in Core Data.

• The whole data model with relationships and properties is quite powerful. With this data model, one can represent many data sets in a simple manner, such as the example below:

  

  This example shows part of the data model within Sapphire pertaining to TV shows, where a TV shows contains multiple seasons, each of which contains multiple episodes. Additionally, an episode contains one or more sub-episodes, to handle the case where a single file or DVD contains multiple episodes. Lastly, the show and season objects extend from a superclass CategoryDirectory, which contains some common properties to all collections.
• Since the relationships are defined, they can be automatically maintained. In the above example, if an episode’s show relationship is set to a particular TVShow object, that show’s object will automatically have the episode added to its episodes relationship.
• Delete rules can be set such that if an object is removed, the delete can cascade to remove other objects as well. This is useful in the case of removing a directory, and all the files and directories contained within it.
• Saving to a file is easy since the details of reading and writing a file are handled by Core Data
• While I didn’t use it, undo management is also built into the system.

So, with all these advantages, why is Core Data not used more often. The answer is that it contains numerous short comings.