Why does iDVD store stuff "all over the place"? Project now broken

Question

Hi all,
did an hour long family movie project, and in the meantime cleaned up my documents folder and deleted some stuff that I thought was internet downloads etc, or extra working files.
Turns out it was the important audio stuff for iDVD!
I've broken my project... the stuff was obviously important, and now when I open this project it has a big broken chain on it.
Why does iDVD store important stuff "all over the place" like that? I mean, it's confusing enough (for newbies) to learn where the events and where the projects are stored, but why does it strip off the sound and store them in documents where ANYTHING could get deleted?

Answer 1

Just to add, an iDVD project should be thought of as a shell, an empty container. It has references to the media files used in it, but does not actually contain these files. The files remain in their normal locations. When you burn to disk, or create a disk image file, iDVD pulls these files just for encoding onto a DVD disk or into a disk image file. It does not really move these files into its project files. Your iMovies, photos and audio files remain where they are. If you move, change, rename or delete any of these files, iDVD will not be able to locate them, and you will see the broken link images.
For this and several other reasons, it is a good idea to leave everything alone and not go deleting any files until you have finished your iDVD project.
Then, when you are ready to burn it to DVD disk, be sure to do a 'Save as disk image' to create a disk image file of the project. This process looks like the burn process, and the encoding will take just as long, but the end result is a self-contained disk image file, not a burned DVD disk.
The advantage of the disk image file is that you will have an exact copy of your iDVD project with all the media files encoded into it. You now can safely delete all the media used in this iDVD project without losing the project. Now you can clean up your documents folder! Deleting all the files used in the project will also save you drive space.
You can save disk image files as backups and can move them to external drives or other computers. You can burn DVD disks from disk image files using Disk Utility or Toast. You don't have to worry about your burned DVD disk breaking/melting or having something spilled on it (kids in the house!). You can always get the disk image file and burn another copy. (Great for the relatives who somehow 'lose' the great DVD you made for them!).
You cannot edit the disk image files however, so you should be creating one only when your project is completely finished.
If you wish to save all your iDVD files while you are working on a project, you can archive your iDVD project. I have not found the need to do this, but the link J Keller gave you for the tutorial explains how to save as archive and as disk image. Obviously, the archive project will be larger since it is saving all the media. Archived projects can also be moved to other drives or computers.
Hope you can recreate your project.
Note to J Keller: the video tutorial was quick and gave the brief how-to and why. Nothing complicated.