(Specification and Description Language) A modeling language used to describe real-time systems. It is widely used to model state machines in the telecommunications, aviation, automotive and medical industries. SDL is used to model the details of a system, which can be simulated and proven, whereas UML is used to model at a higher level of abstraction.
There are three parts to an SDL diagram: the system definition, block and process. The system definition defines the major nodes (blocks) of the system such as clients and servers, while the block charts show more details. The process diagram shows the processing steps in each block. See
state machine and
UML.
SDL Process Diagram
This diagram shows the processing steps within the server of a very simple system that lets the user add two numbers at a terminal. Note that there is more detail in this diagram than there is in the UML counterpart below. (Diagram courtesy of Telelogic, AB, www.telelogic.com)
UML Equivalent
This is the UML equivalent of the process diagram above. Note the difference in the levels of detail. This UML diagram was turned into the SDL above by Telelogic's UML to SDL Translator (see
UML for more diagrams).
(Diagram courtesy of Telelogic, AB, www.telelogic.com)