[Inkscape-devel] SPObject coding

Can anyone give me some pointers on how to implement an SPObject? I'd like to correctly hook the metadata repr's to something that can receive proper signals, etc. Right now the metadata is a giant flaming hack, and it looks like I could really solve a bunch of the bugs by making it act like other repr-based things. Where can I look for some _easy_ examples of how the SPObject stuff works, and what the minimum requirement is for function implementations, etc?