This volume contains the papers presented at the Tenth SDL Forum, Cop- hagen. SDL is the Speci?cation and Description Language ?rst standardized by the world telecommunications body, the International Telecommunications Union (ITU), more than 20 years ago in 1976. While the original language and domain of application has evolved signi?cantly, the foundations of SDL as a graphical, state-transition and process-communication language for real-time systems have remained. Today SDL has also grown to be one notation in the set of uni?ed modelling languages recommended by the ITU (ASN.1, MSC, SDL, ODL, and TTCN) that can be used in methodology taking engineering of systems from requirements capture through to testing and operation. The SDL Forum is held every two years and has become the most imp- tant event in the calendar for anyone involved in SDL and related languages and technology. The SDL Forum Society that runs the Forum is a non-pro?t organization whose aim it is to promote and develop these languages.