Can object databases and relational databases co-exist?
A. Absolutely and this is what you usually see. Typically, people using object databases carve out the part of their IT systems that need high performance on complex data. They then will do other processing, such as back office analysis, using an RDBMS. Often the object database data is transferred to the relational database during quieter processing times. I like to characterize this as database diversity — using the right tool for the right purpose. For some examples, take a look at Architectures using databases in the middle tier.
