Lewis et al. wrote down the original idea in 2020: combine the parametric memory inside a language model with non-parametric memory pulled from somewhere else. It solved a real problem. Models could finally stop making things up about Tuesday.
Most enterprise RAG since then has stopped at that paper. Vector search plus an LLM. Predictable failure modes when knowledge has to be composed across sources, when claims contradict, when half the documents are eighteen months old and no one bothered to mark them as such.
Our research line — Retrieve Is Not Enough — is about what a retrieval system needs once you accept that similarity search is the floor, not the ceiling.