SDL (Specification and Description Language) is a graphical specification
language standardized by ITU (International
SDL, defined in Z.100, has been evolving since the
first recommendation in 1980. Previously, every fourth year an updated revision of the
language standard was adopted. In 1992 Object Oriented features were
included in SDL. The standard adopted in 1996, called SDL-96, introduced only minor
The current version of SDL (SDL-2010) is available from the site Z.100 - Z.109:
Specification of Description Language. Note that not all features and concepts of this recommendation is supported by Cinderella SDL.
Although SDL is widely used in the telecommunications field, it is
not designed specifically for describing telecommunications
services. Rather SDL is a general purpose specification language for
communication systems and embedded systems.
The graphical notation, the formal semantics, and object-oriented concepts
makes SDL a powerful and versatile language both for systems specification
and their implementation.
The basis for description of behaviour in SDL is communicating extended
finite state machines, represented by processes. A process consists of
a number of states and a number of transitions connecting the states.
Communication between processes is done by signal exchange. Signals can be
exchanged between two processes in a system or between a process and the
environment of the system. The remote procedure and remote variable paradigms
for information exchange between entities in an SDL system are also supported.
The current SDL recommendation includes parts
defined to complement and ease the use of SDL in combination with other
notations, e.g. the combined use of SDL and ASN.1 (Abstract Syntax Notation 1)
Z.105, and a layout
preserving interchange format, CIF (Common Interchange Format)
Z.106. These parts
as well as the Message Sequence Chart (MSC)
is partly supported by Cinderella SDL.
For more information on features in SDL
and information on upcoming events related to SDL and MSC, see also