The core of the DLR's type system is based on passing messages to objects. This isn't exactly a new idea, but focuses on what has always been the intellectual core of object-oriented systems. This simple notion doesn't explicitly talk about types at all, but instead focuses on objects and messages. Every dynamic and static language has its own notion of what a type is - from C#'s static single-inheritance types to Python's dynamic multiple-inheritance types to JavaScript's prototypes. Trying to reconcile all of these different systems at the type level is ridiculously complicated - although maybe something to tackle for DLR v2. Despite their differences at the type level, all of these languages share tremendous commonalities if you view them at the object-based message-passing level.

In order to support a broad range of languages in this kind of a type system, we need to have a standard set of clearly defined messages that all objects can respond to. The set needs to be rich enough to capture all of the unique properties of the different languages that we're working with while at the same time be sufficiently common so that code written in different languages can work together. This is a balance that I'm sure we're going to need to adjust as we bring more languages to the DLR - but I think we have an excellent start and lots of success with our initial four languages.