It would be easy to create an implementation of NxBRE.InferenceEngine.IO.IFactBaseAdapter
that loads facts from OrientDB, but that would not address the issue of going "above the limits of the physical RAM". Indeed, NxBRE would then merely load all the facts from OrientDB in its own memory and... you imagine the rest.
To achieve your goal, an alternative implementation of NxBRE.InferenceEngine.Core.FactBase
would be needed: it would actully have alternative implementations for strategic internal methods like StoreFactForIndividualValue
or Select
that would hit OrientDB instead of its working memory.
So I'd say: it's desirable, it's possible and it's not trivial :)