Part 2: Controlling the Telelogic Tau Simulator UI

In this step we use the Tau Simulator UI to explore the behavior of our MSC model. We demonstrate how to control the Tau Simulator UI and observe the textual execution trace that corresponds to the input MSC model.

The Tau Simulator UI window has a buttons panel (left), a text output panel (right) and a command entry field (bottom). The text output panel displays the execution trace. The Tau Simulator is an interface to the automatically synthesized executable model produced by the KLOCwork MSC to SDL Synthesizer.

The model consists of several concurrent processes (one for each instance in the input MSC model). The processes exchange signals, in accordance with the input MSC. Each process in the synthesized model performs transitions between internal states.

1. Click the Transition button in the buttons panel to perform a single transition of the model. The activities of the model are reported in the text output panel.
2. Click the Transition button again. The Simulator UI opens the Path Selection dialog.



The input MSC model is non-deterministic because it does not provide enough information about the logic behind the actions of the User. According to the model, the User can either send the Request message or the Done message to the Server. The model does not specify how the User makes the choice between these two messages. The KLOCwork MSC to SDL Synthesizer propagates this non-determinism to the executable model. The Telelogic Tau Simulator uses the Path Selection dialog to ask the user which of the alternatives of a non-deterministic choice to take.

3. Explore various alternatives of the non-deterministic choice by selecting a number in the Path Selection dialog and clicking on the Show button.



The Tau MSC Editor appears and the corresponding message is highlighted.

4. Select the first alternative by double clicking on the line with number 1 in the Path Selection dialog. This corresponds to sending the message Done from the User to the Server. The Simulator Trace is displayed in the text output panel.



5. Click the Transition button until the Simulation trace displays the line "No process instance scheduled for a transition". This complete Simulator trace is presented below. The trace consists of 4 transitions (from the line "*** TRANSITION START" to the line "*** NEXTSTATE "). Transitions are performed by different instances of the MSC model (see the name of the instance in the second line in each transition section after the keyword PId). The transition section also contains the input signal, or the transition trigger (see the name of the input signal in the fourth line of transition section after the keyword Input).

Welcome to the SDL SIMULATOR. Simulating system SynthesizedModel.

Command : Next-Transition

*** TRANSITION START

* PId : USER:1

* State : start state

* Now : 0.0000

* OUTPUT of INIT to SERVER:1

Decision with ANY

1 go

1 ? show

2 go

2 ? show

Command : 1

* OUTPUT of DONE to SERVER:1

*** STOP (no signals were discarded)

Command : Next-Transition

*** TRANSITION START

* PId : SERVER:1

* State : start state

* Now : 0.0000

*** NEXTSTATE REQUEST_INIT_2

Command : Next-Transition

*** TRANSITION START

* PId : SERVER:1

* State : REQUEST_INIT_2

* Input : INIT

* Sender : USER:1+

* Now : 0.0000

*** NEXTSTATE A_LOOP_1

Command : Next-Transition

*** TRANSITION START

* PId : SERVER:1

* State : A_LOOP_1

* Input : DONE

* Sender : USER:1+

* Now : 0.0000

*** NEXTSTATE REQUEST_INIT_2

Command : Next-Transition

No process instance scheduled for a transition

6. To restart the simulation, from the File menu, choose Restart.

Summary

In this part of the exercise we demonstrated how to use the KLOCwork MSC to SDL Synthesizer to simulate MSCs. We explored the behavior of our MSC model using the textual trace of the Telelogic Tau Simulator UI.

In the next two parts of this exercise we will explore more powerful ways to visualize execution traces using the KLOCwork MSC to SDL Synthesizer and Telelogic Tau.