Message Sequence Charts (MSC) have had an unanticipated success, both with SDL, on its own and in conjunction with other methods and tools. Major tool vendors now offer both SDL and MSC in their tool set. This timely volume reports on the recent developments in this expanding field. Several papers deal with language issues, tools and methods for effective use of MSC. Advances in "SDL technology" are discussed, and several papers deal with the early stages of product development and how SDL may be complemented by other methods, such as OMT, to improve problem understanding and make better SDL designs. New developments in the areas of tools for verification, validation and testing are also included, together with a large number of papers on applications.