Today I read the CBDI's review of the Microsoft Whitehorse technologies shown at the Professional Developers Conference in October.  What I hadn't noticed at the PDC about this is the idea that the Microsoft System Definition Model diagrams and elements are not only edited in the same tool as the code, they are first class artifacts integrared with the code.  There is no round tripping, it all happens at the same time.  Think of it.  A modelling tool that doesn't need round-tripping.  This has the possibility of removing the concept that modelling is for documentation purposes only and making it actually useful in reducing development time.