SDL is a design and implementation language dedicated to advanced technical systems (i.e., real-time systems, distributed systems, and generic event-driven systems where parallel activities and communication are involved). Typical application areas are high- and low-level telecom systems, aerospace systems, and distributed or highly complex mission-critical systems.

SDL has a set of specialized characteristics that distinguishes it from other technologies:

• standard—SDL is a nonproprietary internationally standardized language (ITU–T standard Z.100 and Z.105).
• formal—SDL is a formal language ensuring precision, consistency, and clarity in the design that is crucial for mission-critical applications (e.g., most technical systems). graphical and symbol-based—SDL is a graphical and symbol-based language providing clarity and ease of use. An SDL design is both an implementation and its own documentation.
• object-oriented (OO)—SDL is a fully OO language supporting encapsulation, polymorphism, and dynamic binding. Moreover, SDL extends the traditional data-oriented OO class concept by customizing it for technical applications and introducing OO concepts for active objects (e.g., systems, blocks, and state machines).
• highly testable—SDL has a high degree of testability as a result of its formalism for parallelism, interfaces, communication, and time. The quality and speed improvements are dramatic compared to traditional nonformal design techniques.
• portable, scalable, and open—SDL is portable, scalable, and open. SDL implementations are independent of cross compilers, operating systems, processors, interprocess communication mechanisms, and distribution methods. A single SDL implementation can be used for many different target architectures and configurations.
• highly reusable—SDL provides a high degree of reuse. Because of visual clarity, testability, OO concepts, clear interfaces, and abstraction mechanisms, SDL design has a much higher degree of reusability than any other type of design or implementation.
• efficient—The formalism and the level of abstraction that is provided by SDL make it possible to apply sophisticated optimization techniques for cross-compilation.