So one would have one OGM specific logging category (similar to org.hibernate.SQL in ORM) which when set to the right level would log the data store interactions, right?

I guess in the case where there is a "simple" wire protocol (for example the Mongo REST API) you would probably like to log the JSON request, right? More problematic would be pure programmatic APIs. I guess Infinispan would fall into that. Would you expect the log method calls to the Infinispan Cache with the provided parameters?