erator alt operator (alternative) expression separator Figure 5.10 The inline MSC operators used in testlinline.msc This MSC represents the following behavior expected from the V.76 SDL model: 1. one connection phase, 2. followed any number of times (between 0 and infinite) by the repetition (operator loop <0, inf>) of data transfers from A to B or (operator alt) from B to A, 3. followed by the disconnection phase initiated by A or (second alt operator) initiated by B. 5.2.3.2 Use the MSC to check the SDL model A. Start the Validator as indicated in Section 5.2.1.2, and enter the command: load-msc testlinline.msc B. Select Commands > Toggle MSC Trace. C. Press the Navigator button in the Explore group. D. Using the Navigator, execute an SDL scenario matching the loaded MSC (when there are two possibilities, select the left one): for example, establish DLC number 0, then transmit data 86, and then release DLC number 0. E. After around 40 transitions, the Navigator window displays: No down node - MSC testlinline verified, as shown in Figure 5.12. It means that one of the signal sequences present in the loaded MSC has been simulated. The Navigator also indicates which MSC operators have been followed and which branch has been taken in each alt operator. You could press the button Top in the Explore group to go back to the initial SDL model state, and try to verify other paths, for example, no data transfer, or a data transfer from B to A and SO on. F. Exit from the Validator. Automatic Observation of Simulations 121 MSC test1inline block block block dataLink DLCaSU DLCa_2 dataLink_1 DLCb_3 DLCbSU L_EstabReq V76frame V76frame (SABME (.0.) ) L_Establnd (0) (SABME : (.0.) ) operator L_EstabResp V76frame V76frame L EstabConf (0) (UA : . . 0 .)) (UA : (.0.) ) loop <0, inf> L_DataReq V76frame (0,86) V76frame (I : . . 0 86, 15 .)) L_Datalnd alt operator ( I ( ( 0, 86,15 .) 0,86) (alternative) L_DataReq V76frame (0,39) V76frame L Datalnd (0, 39) (1: 0, 39, 15. (1: (. 0, 39, 15 L_ReleaseReq V76frame V76frame (DISC : (. 0 .))