nst_DL located on top of datalink in the MSC is not supposed to match any SDL name. Then, when using an MSC as an observer, only the following symbols, depicted in Figure 5.64, are dynamically checked during simulation: Signal input and output and their parameter values, Timer set, reset and timeout. retry1 inst_dataLink inst_1_DLCa datalink Timer set: checked DLCa/DLC(1) T320(12.0) Timer reset: checked Signal output: checked v76frame(sabme : (.0.)) Signal parameters: checked T320 (12.0) Signal input: Timer timeout: checked checked Figure 5.64 The MSC symbols checked during observation The other symbols present in the MSC, shown in Figure 5.65, are ignored. 5.3.4.3 The syntax for MSC signal parameters A special notation has been introduced for signal parameters in observer MSCs. An example is shown in Figure 5.66. In this example: The first occurrence of sig means that the output of sig is expected from BTS with value 17 as first parameter, cyan as second parameter and True as third parameter. In the second occurrence, sig is expected with any value as first parameter, cyan as second parameter and any value as third parameter. In the third occurrence, sig is expected with 17 as first parameter, cyan, black or yellow as second parameter and True as third parameter. In the fourth occurrence, sig is expected with a value between 4 and 16 as first parameter, cyan as second parameter and False as third parameter. 154 Validation of Communications Systems with SDL retry1 inst_dispatch_a Create: ignored inst_1_DLCa DLCa/DLC(1) L_EstabReq(0) L_ReleaseReq(0) Coregion: ignored Condition: ignored ready Action: ignored "n320cnt=3" Stop: ignored Figure 5.65 The MSC symbols not checked during observation system test1 synt_msc my_BTS sig(17, cyan, True) any value NEWTYPE colors LITERALS sig( *, cyan, * ) cyan, magenta, one value in the list yellow, black ; sig(17, ( cyan, black, yellow ), True) ENDNEWTYPE; between 4 and 16 SIGNAL sig (Integer, colors, Boolean) ; sig( 4..16, cyan, False) Figure 5.66 Example of observer MSC with s