L_DataReq(0, 55) to DLCa. O. Double-click on the next transition: the Navigator displays the observer report depicted in Figure 5.38, because uData contains 55. 5.2.7 More details on observer processes Note that several observer processes may be used at the same time in the Validator. 5.2.7.1 Using an observer process to test the state of a process The observer process obs2 represented in Figure 5.39 detects when the state of process dispatch in block DLCa is equal to waitUA. Automatic Observation of Simulations 135 Navigator Next 8: Next 9: OUTPUT from ENV. OUTPUT from taReq Signal : L_DataReq Signal : L_D: lock DLCa>> Receiver : <<Block DLCa>> Receiver : <<E dispatch:1 dispatch:1 0, -55 Parameter(s) : 0,55 Parameter(s) Figure 5.37 The Validator ready to transmit L_DataReq(0, 55) to DLCa Navigator Up 1: Transition START Pld : <<Block DLCa>> dispatch:1 State : ready Input : L_DataReq Sender : env Parameter(s) : 0, 55 No down node Assertion is false: uData in A=55 Figure 5.38 The condition has been detected by the observer obs1 process obs2 testing SIGNALSET; disp1:= True; (GetState(disp1) = 'waitUA'); GetPid('dispatch', 1) Priority 200 Priority 1 disp1 Pid; Report testing ('process dispatch in block DLCa is in state waitUA') Figure 5.39 Testing if a process is in a certain state 136 Validation of Communications Systems with SDL 5.2.7.2 Using an observer process to detect process creation and stop The observer process obs3 represented in Figure 5.40 detects when the instance of process dispatch in block DLCa is stopped (this does not occur in the V.76 SDL model). process obs3 testing SIGNALSET; disp1:= True; terminated(disp1); GetPid('dispatch', 1) Priority 200 Priority 1 disp1 Pid; Report testing ('process dispatch in block DLCa is dead') Figure 5.40 Detecting process instance stop 5.3 CASE STUDY WITH OBJECTGEODE 5.3.1 Simulate with stop conditions 5.3.1.1 Detect DLC establishment We want to detect that a DLC is established. This means, in our V.76 SDL model, that: instance 1 of process DLC in block DLCa is in st