I was drawing a comparison between the Kdb runtime and the Erlang runtime, because the OP seems to be conflating the ability to emulate relational features at the application level with first-class support for relational semantics as in a relational database. Support for relational semantics can be emulated via programming languages with sophisticated runtimes like Erlang, but I wouldn't classify any database supporting a Turing complete language with a sophisticated runtime as a relational database.