I'm ok with this. Some thoughts:
- We should state that geometry is not allowed in a !DATA section. Any geometry that does exist is an error and either should be ignored or will produce undefined results.
- We don't want to drop the ! for consistency. 0 FILE has been around for a long time, so it's not likely to show up in any files with another meaning. 0 DATA and 0 : could easily show up in existing files.
- We should probably have an example where the !DATA section isn't at the end of the MPD.