th developed by Telelogic2: ObjectGeode Version 4.2 for Windows Tau SDL Suite Version 4.0 for Windows The Unix versions of these tools are very similar to their Windows version. The main difference is the way they are launched: it is generally performed by double clicking on an SDL file in Windows and by typing a command in Unix. The V.76 SDL model used in the book and its associated files can be downloaded in ObjectGeode and Tau SDL Suite formats onftp://ftp.wiley.co.uk/pub/books/Idoldi/. 2 ObjectGeode has been developed by Verilog, with France Telecom R&D (former CNET) know-how. Then, in 1999, Telelogic has acquired Verilog. Quick Tutorial on SDL For readers not familiar with SDL, this chapter presents the most frequently used constructs of SDL-92. A detailed step-by-step tutorial on SDL-92 [SDL92] and a presentation of SDL-2000 are provided in [Doldi01]. 2.1 STRUCTURE OF AN SDL MODEL 2.1.1 System, block and process SDL provides the following entities to structure a description: system: top level, outermost construct; block: must be contained in the system or in a block; process: must be contained in a block; service (optional): must be contained in a process; procedure (optional): can be placed anywhere. Figure 2.1 shows an example of a system containing three blocks. system syst1 (dlc2su) (dlc2su) DLCaSU DLCbSU (su2dlc) (su2dlc) block1 block2 (V76frames) (V76frames) DLCaDL DLCbDL (V76frames) (V76frames) block3 Figure 2.1 System systl Figure 2.2 shows that blockl contains two blocks. Figure 2.3 represents the contents of block1_1 and block3. Block1 1 contains one process, and block3 contains two processes. The state machines contained in processes (or services) instances communicate together or with the environment by transmitting and receiving signals (or remote variables or procedures) through channels and signal routes. Validation of Communications Systems with SDL: The Art of SDL Simulation and Reachability Analysis. Laurent Doldi © 2003 John Wiley & Sons, Ltd ISBN: 0-470-85286-0 10 Validation of Communica