The only thing I have to add at this point is that with frameworks such as Cayenne, there is less benefit in trying to put all data in the same database, so perhaps in the future we're going to see more rather than less applications sitting on top of heterogeneous databases?
Converting databases to the same underlying database yields, hopefully, no visible change to the application and it is harder to get that sort of work funded in a project. -- Øyvind Harboe http://www.zylin.com - eCos ARM & FPGA developer kit
