Since more than two decades, a lot of work has been achieved around Model Driven Engineering (MDE). One of the main goals of MDE is to improve the software development process productivity thanks to a generative approach. Many MDE environments are available today. These environments allow a designer to specify object oriented meta-models. Meta-models structure can be specified through the definition of statically typed entities and entities relationships. Even if some of these environments also enable specifying meta-model invariants and behavior, two important issues remain unsolved: – regarding meta-model execution, only limited capabilities are exhibited and the development process still relies on code generation into a mainstream language for validation; – because of the generative approach, no causal connection is possible between a meta-model and its conforming models. To deal with these issues, we decided to use Smalltalk as a MDE environment mainly because it provides us with a way of implementing meta-model execution. A Smalltalk system can be used as a modeling system providing out-of-the-box an infrastructure for meta-modeling, browsing, and testing. It also provides a rich system which enables implementing realistic prototypes. Moreover Smalltalk implements a Meta Object Protocol which maintains a causally connected modeling architecture. Smalltalk is known as very powerful for the agile implementation of systems, for continuous testing and finally for early validation through prototyping. Unfortunately, Smalltalk is not a mainstream language and can be rarely used as the final platform. This article shows that it is possible to successfully use Smalltalk as a MDE environment even if the target system is not implemented in Smalltalk. Indeed, the software development process can be adapted to benefit from early validation and to be able to automatically produce or update a target system. For validation purpose, we have developed the Platypus tool, which enables static typing in Smalltalk and makes this MDE approach possible.