Object/Relational Mappings (ORM’s) are in the wrong place in the architecture.
An application should have minimal impedance mismatch with the persistence of its own data. External or ancillary systems should bear the cost of mapping between paradigms. If you want to access application data in a relational way for reports, do the mapping for the report.
Squealer is a simple, declarative language where the mapping from the tree structure of MongoDB to the tuple space in mySQL can be scripted.
