Can I use a persistence manager to access an existing data source?
No. The persistence manager interface was never intended as being a general SPI that you could implement in order to integrate external data sources with proprietary formats (e.g. a customers database). The reason why we abstracted the PM interface was to leave room for future performance optimizations that would not affect the rest of the implementation (e.g. by storing the raw data in a b-tree based database instead of individual file).
