As Cavalli and Sarma astutely remarked in the introduction to this volume, it is quite remarkable that SDL '97 may have the first participant younger than SDL itself. SDL '97 provides the opportunity to reflect the course SDL has taken and why it has been successful over two decades where other languages addressing the same market have failed.SDL now also has a permanent companion in MSC (Message Sequence Charts). MSC today is a language in its own right and has its areas of application both in conjunction with SDL and independently or in combination with other techniques. MSC has strong structuring concepts to specify message sequences for large systems and can be used to develop scenarios, which is extremely useful for test and design environments. The SDL Forum today really is the SDL and MSC Forum.