Atom2Yaml
why the lucky stiff: Now, I'll tell you upfront. This match is rigged. The deck is stacked against XML. I just threw together an Atom2YAML converter. Atom = 12 MB. YAML = 6 MB. I only have to do 50% of the work. And these are awful YAML documents. Give me an afternoon and we'll be down to 5MB with some fragrance.
The goal is to support these queries. It will be interesting to see how _why handles the second one given that he is currently cheating on the content element. ;-)