SDL has its origin in the telecommunications area and has been especially embraced by this industry. Much of the research work on this formal langu age has been carried out in the labs of the Danish telecommunications company, TeleDanmark, Swedish Telecom, and Telia Research in Sweden. Both firms sell suites of tools that let users analyze and design systems graphically as a series of charts, verify the correctness of these diagrams, and automatically generate C code. These tools are being used in companies that span the telecommunications, aerospace, defense, and automotive industries to develop products as diverse as factory automation systems, PBXes, and artificial kidneys. SDL design tools can simulate the functioning of a system.
Any ambiguity is detectable as an error.
The term is defined by the International Telecommunications Union in its recommendation Z.120. An MSC shows the sequences of messages sent between the components in an easily readable form, with the components arranged as vertical columns and the messages as horizontal rows joining the columns. The time axis is vertical. MSC is useful in several phases of the specification of an interactive real-time system. Designers use MSC at the very beginning of a project as a notation to capture the user's requirements.