In this stimulating interview on InfoQ, which is one of Sadek Drobi's better interviews, Erik explores the dualistic database design space along 3(+1) dimensions.
http://www.infoq.com/interviews/meijer-big-data
There's a pretty explosive growth in new database engines, so this talk is highly relevant. Just Google for "new databases" and you'll find a nice diagram.
Erik also hints at interesting ideas along the way.
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