I've been experimenting with a library called `refmt` which does the Object Mapping part, but explicitly not the Relational part. It's still experimental, but you might like it, and test coverage is shaping up nicely.

The idea is by focusing completely on making Object Mapping consistent and powerfully customizable, and then composing that with either serialization formats or relational storage, we'll get good things. Right now we seem to be at and awkward hump of complexity where every new DB binding ends up implementing their own object mapping, increasing everyone's complexity, overhead, and decreasing reusability of code; refmt will hopefully represent a break from that.

https://github.com/polydawn/refmt