My aim is to create a pluggable storage engine architecture for Derby, so that the default store implementation can be replaced with alternative storage engines. I have created my own storage engine which I would like to use with Derby's SQL layer, so that is a motivation. But I also think that this will benefit the community, and could lead to a pluggable storage engine architecture similar to that of MySQL.
I am not yet sure where the storage engine boundary should lie. I would welcome input in this area.