Type Systems for DSLs

Non-trivial DSLs, as they are possible with today's tools, often include expressions. Once you have expressions, you usually also have several different (primitive and user-defined) types that need to be type checked with the help of a type system. In this session, I will explain what type systems are, how they are different from "normal" constraint checking, and which typing rules you will often need. I will then illustrate the concepts with MPS and Xtext (using the XText typesystem framework).