meout, Process instance create and stop, Global MSC reference (without substitution and gates), Condition (if Define-Condition-Check is on, default is off). The other symbols present in the MSC, shown in Figure 5.25, are ignored. MSC retry1 dataLink DLC_1 dataLink_1 action 'n320cnt := 3' L_EstabReq (0) L_ReleaseReq (0) coregion Figure 5.25 The MSC symbols not checked dynamically 5.2.5.3 The MSC signal parameters The values of the signal parameters in an MSC to be verified can be omitted: in that case, they are not checked. Automatic Observation of Simulations 129 system lights control [ response ] order ] NEWTYPE colors LITERALS red, orange, green; ENDNEWTYPE; SIGNAL order(colors, Natural), response(color Boolean, Integer); Figure 5.26 The SDL model lights We consider the SDL model lights shown in Figure 5.26: it can receive a signal order, having one parameter of type colors and one parameter of type Natural. The signal response has one parameter of type colors, one parameter of type Boolean and one parameter of type Integer. The Validator automatically generates test values for each incoming external signal such as order. The default test values are 0 and 55 for Natural parameters. During simulation, the Validator makes a combination of all possible test values, to test all combinations of parameter values in the signals received by the SDL model. For example, in Figure 5.27, the signal order is shown with all test value combinations created by the Validator: the first parameter of type colors takes three values red, orange or green, and the second parameter of type Natural takes the values 0 or 55. Therefore, we have 3 x 2 = 6 possibilities: (red, 0), (red, 55), (orange, 0) and SO on. Navigator Up 1: Transition START Pld proc1:1 State start state Next 1: Next 2: Next 3: Next 4: Next 5: OUTPUT from ENV. OUTPUT from ENV. OUTPUT from ENV. OUTPUT from ENV. OUTPUT from ENV. Signal order Signal order Signal order Signal order Signal order Receiver proc1:1 Receiver proc1:1 Receiver proc1:1 Receiver proc1:1 Receiver p