There's already lots of different types of "database systems" floating around. Map/Reduce approaches to large-scale data processing has been getting most of th

There's already lots of different types of "database systems" floating around. Map/Reduce approaches to large-scale data processing has been getting most of the hype in the F/OSS space and columnar approaches in the enterprise spaces. An area that is finally starting to get some love are approaches like Mark Logic's "XML contentbase" approach -- native XML data store that's wicked fast. Of course, I'm biased but I think MarkMail (http://markmail.org/ http://markmail.org/) is a pretty slick, public example of it in action.