This volume contains the papers presented at the 12th SDL Forum, Grimstad, Norway. The SDL Forum was ?rst held in 1982, and then every two years from 1985. Initially the Forum was concerned only with the Speci?cation and Description Language that was ?rst standardized in the 1976 Orange Book of the Inter- tional Telecommunication Union (ITU). Since then, many developments took place and the language has undergone several changes. However, the main...