In 1998 I built the Genre Browser — possibly the first hybrid collaborative-filtering and expert-system engine for music discovery: I’ve never found an earlier one. Collaborative filtering represents people and music as vectors and recommends by proximity. It works, and it fails in specific, predictable ways: it collapses toward the popular, bridges incorrectly across semantic clusters, overindexes early data, can’t explain itself, and can’t tell when it’s wrong.
I’m also a DJ, so I knew things about why a recommendation lands that the statistics couldn’t see. So I encoded that as a rule layer over the similarity engine, and made a dramatically better system.
Vector-space operations plus expert rules (aka skills and harnesses) is exactly where applied AI work sits right now. Embedding-and-retrieval systems are direct descendants of collaborative filtering: Magpie runs on pgvector for the same reason the Genre Browser ran on similarity. And the practical job is still the same job — knowing where the statistics break, and building real domain knowledge into the structure around them. Schemas, evals, constrained extraction, retrieval filters — and the interface, which decides whether any of it reaches a person as something they want. Different vocabulary, same problem.
I’ve been doing that for thirty years. The engine changes every eighteen months. The fundamentals of building around it to make it useful haven’t changed at all.