I don't believe code _is_ the documentation. I've thought of information systems for code, I once used OpenGrok to parse a large codebase and try work out how

I don't believe code _is_ the documentation. I've thought of information systems for code, I once used OpenGrok to parse a large codebase and try work out how it works. But it's undirected learning. I think question answering would be useful: "Where should I change the code to insert behaviour that changes X, Y, Z behaviours"