f signal v76frame by block datalink. Also the window named MSC Hierarchy v76_and shows in bold which scenarios can accept events: as we are in data_a2b_0, the other scenarios located after it such as disc_or are not yet ready; data_a2b_0 must be finished first. G. Finish replaying the simulation scenario until its end (Step 41) by pressing the Redo or Redo: All buttons. You should see the line: SUCCESS state reached in scenario v76_and It proves that the SDL simulated behavior is included in the expected behaviors described in the observer MSC v76_and. You can now simulate manually other scenarios and try reaching again the success state in the MSC observers. Chapter 7 will show you how the Simulator can discover automatically such scenarios. 5.3.4 More details on MSCs 5.3.4.1 The operators used in MSCs To represent a more complex behavior than a single basic scenario, operators specific to Object- Geode can be used to create a hierarchy of MSCs. This is similar to the HMSCs used in Tau. The operators are: 150 Validation of Communications Systems with SDL geodedit - MSC: xid_a File Edit View Navigate Tools Window Help MSC: data_a2b_0 data_a2b_0 inst_dica inst_datalink inst_dlcb datalink 1* Transfer of data 86 through DLC number 0: */ L_DataReq(0,8 v76frame( i: (. 0,86,15 )) v76frame( i: (.0,86,15 .) __Datalnd(0,86) MSC Hierarchy: ¥76 and v76_and cnx_0 data_repeat disc_or data_or disc_0_by_a disc_0_by_b data_a2b_0 data_b2a_0 MSC: xid a xid_a Inst_dica inst_dlcb BLOCK / BLOCK / v76test v76test /dlca /dlcb /* Exchange identification (XID): */ I setparmreg I_setparmind I_setparmresp I_setparmconf Figure 5.59 Tracking the two MSCs v76_and and xid_a during simulation AND: sequence OR: alternative REPEAT: repetition 0 to n times EXCEPTION: description of behavior expected after an error PARALLEL: independent execution of several MSCs. We will only detail the most used operators: AND, OR and REPEAT. Automatic Observation of Simulations 151 The operator AND is used to split one long scenario into two, three or more shorte