Advanced users often find themselves restricted by the limited facilities of most UML CASE tools when they want to do complex manipulations of UML models, e.g., apply design patterns, generate code for simulation and validation etc. We describe UMLAUT, a freely available UML transformation framework for manipulating UML models. These manipulations are expressed as algebraic compositions of reified elementary transformations. They are thus open to extensions through inheritance and aggregation. To illustrate the interest of our approach, we show how the model of a UML distributed application can be automatically transformed into a labeled transition system validated using advanced protocol validation technology.