2, if you simulate the SDL sequence sA, sC and sB, you get an error (or you do not get a success), because sB was expected before sC. test_time inst_1 inst_2 proc1 proc2 Figure 5.72 Observer MSC with two instances If set to local, the ordering of events is local to each instance present in the observer MSC. In the same example, if you simulate the SDL sequence sA, sC and sB, you do not get an error (or you get a success), because each instance procl and proc2 are observed separately. The Automatic Observation of Simulations 159 only things checked are that sC occurs after sA (you get a success) and that sZ occurs after sB (you get another success). 5.3.5 Simulate with GOAL observers You will create and simulate a GOAL observer checking that the DLC establishment works, that is, after an establishment request an establishment confirmation occurs. In other words, the observer must check that: block DLCa in our model receives signal L_EstabReq, signal L_EstabConf is transmitted by block DLCa and the parameter of L_EstabConf (the number of the created DLC) is equal to the parameter of L_EstabReq (the number of the DLC to create). This could have been checked by the MSC shown in Figure 5.73, except that it only works for one parameter value: one MSC might be used for 0, another for 1 and SO on. obs_ex1 inst_dlca l_estabreq( 0) I_estabconf( 0) Figure 5.73 An observer MSC cannot memorize values 5.3.5.1 Create the GOAL observer A. In the Editor, select File > New > GOAL Observer. Select untilted1.obs, do File > Save As and enter obs_ex2.obs. B. Press the Observation palette button and name the observation v76test. C. Press the Observer palette button to create an observer and name it obs1. D. Select the observation v76test and press the Text palette button: this creates a PR Declara- tion. Your Framework view should look like Figure 5.74. FrameWork F:ADONNEES\IRANS v76:est PR Declaration Figure 5.74 The Editor Framework view 160 Validation of Communications Systems with SDL E. Double-click the PR Declaration and enter: p