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?

Yes, I think that'd make sense.

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?

Yes, it could work like that for the CouchDB dialect (which uses JAX-RS/JSON) and Neo4j (where we have the Cypher query language, at least partly). For MongoDB we don't use a REST API but a "normal" Java API which then sends requests to the server in a binary format. I'm not sure whether these could be accessed and be made readable in a sensible way. So MongoDB might fall into the API category as well.

Would you expect the log method calls to the Infinispan Cache with the provided parameters?

It's a good question. It's not perfect but it's the best I can see atm. Same for Neo4j btw. when we don't use Cypher but programmatic calls on the Node API. Or do you have any other idea, Emmanuel Bernard?