I took this to mean that what he is replacing is a single XML file whose content is a tree of element nodes. Every time you have to make a change to that file (

I took this to mean that what he is replacing is a single XML file whose content is a tree of element nodes. Every time you have to make a change to that file (changing, removing or adding children nodes within the file) you would have to store a new copy of the file. The most efficient you can get is to store just the text diffs using git or something. But what he replaces it with is a git object store. Each xml-node becomes a git object. They each point to a parent (just as git commits point to a parent commit). Now writing to this datastore means adding a new node to the git object database and changing the parent references. Where git stores commits that are related sequentially in time, this stores nodes in a tree relationship that IS the document. If he's not talking about this then I'd like to officially take credit for my weird idea right now.