Separation of concerns is a basic engineering principle that is also at the core of object-oriented analysis and design methods in the context of the Unified Modeling Language (UML). The UML gives the designer a rich, but somehow disorganized, set of views on her model as well as many features, such as design pattern occurrences, stereotypes or tag values, allowing her to add non-functional information to a model. Aspect-oriented concepts are applied to manage the multitude of design constraints. However, it can then be an overwhelming task to reconcile the various aspects of a model into a working implementation. In this paper, we introduce our UMLAUT framework as a tool for “weaving” aspects when modeling with the UML. This is accompanied with an example of a distributed multimedia application, applying two different weavings: one for implementation, the other one for validation based on model checking technology.