[UPDATE]: I've posted a tweaked version of this diagram here.
Continuing my recent interest in making diagrams of things, this weekend's project was a visual representation of what the global state files of apt and dpkg are, what's stored in them, and how they're manipulated. As before, this includes only the core part of the system (ok, I squeezed aptitude in there too), for the simple reason that I'm not smart enough to include more stuff in the diagram without making it utterly illegible. As it is, it's already pushing the boundaries of how much you can fit on a single page of paper:
This image is also available in svg and pdf formats. Be warned, though, that the SVG might display oddly in anything but Inkscape, and the PDF only displays correctly in Acrobat Reader. If you want to print off a copy without wasting toner, if you don't have a program capable of printing the above, or if gradients offend you, you can also download a simpler version of the diagram:
Unlike the last diagram I produced, this one was made in Inkscape. It took pretty much the whole weekend, most of which time I spent learning features of Inkscape that I didn't end up using. Oh well. I've come to the conclusion that Inkscape is an amazing graphics program and an utterly terrible diagram editor. Although to be fair, it seems to be one of the best, if not the best, diagram editors in Debian; also, if you slog through it and you have more graphical talent than me, the diagrams will look very good.
[EDIT]: fixed an oversight in the first version of the diagram (apt-get also writes the extended_states file).