This volumecomprises the ?nal versionsof the technicalpapers presented at the UML 2004 conference held in Lisbon (Portugal), October 11-15, 2004. UML 2004 was the seventh conference in a series of annual UML conferences. The series started in 1998 and was located at Mulhouse (France); the following years saw the conference move to Fort Collins (USA) in 1999, York (UK) in 2000,Toronto (Canada) in 2001,Dresden (Germany) in 2002,San Francisco (USA) in 2003, and now Lisbon (Portugal) in 2004. During this time, the UML conference became one of the leading conferences in the area of object-oriented modeling. While in the ?rst years the focus of the conference was on the scienti?c investigation of the Uni?ed Modeling Language (UML), which had just been adopted by the Object Management Group (OMG) at the time, the focus has changed in recent years to innovations in techniques such as metamodeling, model transformations, model validation and veri?cation, aspect orientation, and beyond. Many recent research activities have been especially stimulated by the Model Driven Architecture (MDA) initiative, started in 2000 by the OMG. The goal of MDA is the de?nition of a framework to enable the development of software purely based on models. In order to re?ect the changes of recent years, the conference series UML will be continued, from 2005 onwards,under thenameMODELS(MOdelDrivenEngineering,Languagesand Systems). The call for papers for UML 2004 encouraged authors around the world to submit 157abstractsand 135technicalpapers. Eachsubmissionwasreviewed by at least three referees, in most cases by four.