 Random-Walk performs this repetition automatically. To illustrate this: A. Restart the Validator. B. Select Options1 > Show Options. The Validator displays: Random walk options Search depth : 100 Repetitions : 100 It means that maximum 100 transitions will be executed from the starting step and that the random simulation will be repeated 100 times. It is similar to 100 times the sequence: Random-Down 100 170 Validation of Communications Systems with SDL C. To stop the simulation after the first error, enter in the Validator command line (can be abbreviated to d-r-a -): Define-Report-Abort D. Press on Random Walk to start the random simulation: the Report Viewer appears. Double- click on 1 ImplSigCons to expand the report, as shown in Figure 6.3. You may hit a different error. Report Viewer 1 report 1 ImplSigCons Warning: Implicit signal consumption of signal L_ReleaseReq Sender: <<Block DLCa>> dispatch: 1 Receiver: <<Block DLCa>> DLC:1 Depth: 52 Figure 6.3 The Report Viewer after the random walk E. Double-click on the warning in the Report Viewer to generate the MSC trace corresponding to the error: signal L_ReleaseReq has been transmitted to process DLC in block DLCa, which is unfortunately in state waitUAdisc expecting another signal. The Validator had also displayed the symbols coverage rate at the end of the random walk: Random walk statistics No of reports 1 Gen states : 1093 Max depth : 100 Min depth : 100 Symbol coverage : 81.54 More details on coverage can be found in the Coverage Viewer (Commands > Show Coverage Viewer). 6.2.3 Random simulation with observers You will run the random simulation on the V.76 SDL model monitored by an observer MSC, to automatically check that the simulated behavior complies with the expected behavior. Random Simulation 171 A. Restart the Validator, without saving the options. B. Enter in the Validator command line: Load-MSC test1 msc Now the simulation is driven by the MSC test1: the signals transmitted to the SDL model and the value of their parameters are those present in