A Time Machine for XML

As storage (Main Memory, Disk) becomes cheaper, the amount of available information is increasing and it is a challenge to organize it. A special but very important case is when several versions of some data are collected. Versioned information is very valuable, as it allows going back in time, but it is only valuable if it is efficiently queryable. Nowadays, there are two main, competing versioning paradigms: on the one hand, document versioning (CVS, SVN) can version any kind of document, even binary, but is not aware of what is in the documents other than lines of text.