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Generating and Starting an SDL Explorer
In addition to simulating a system, it is also possible to validate the system using the SDL Explorer. An explorer can be used to automatically find errors and inconsistencies in a system, or to verify the system against requirements.
In the same way as for a simulator, you must generate an executable explorer and start it with a suitable user interface.
What You Will Learn
Quick Start of an SDL Explorer
An explorer can be generated and started in the same way as described earlier for the simulator, i.e., by using the Make dialog and the Tools menu in the Organizer. However, we will now show a quicker way.
- Make sure the system diagram icon is selected in the Organizer.
Click the Explore quick button. The following things will now happen, in rapid succession:
- An executable explorer is generated. Messages similar to when generating a simulator are displayed in the Status Bar, ending with "Analyzer done." This is the same action as manually using the Make dialog and selecting an explorer kernel. If you like, you can verify that an explorer kernel has been used by looking at the tail of the Organizer log.
- A graphical user interface to the explorer is started. The status bar of the Organizer will read "Explorer UI started." This is the same action as manually selecting Explorer UI from the Tools menu.
- The generated explorer is started. The Explorer UI shows the message "Welcome to SDL EXPLORER." This is the same action as manually using the Open quick button and selecting the executable explorer (named demongame_xxx.val (on UNIX), or demongame_xxx.exe (in Windows), where the _xxx suffix is platform or kernel/compiler specific).
The Explorer UI looks like this:
As you can see, the graphical user interface of an explorer is very similar to a simulator GUI, which you have learned to use in the previous exercises. However, the button modules to the left are different and a few extra menus are available.
An explorer contains the same type of monitor system as a simulator. The only difference is the set of available commands.
When an explorer is started, the static process instances in the system are created (in this case Main and Demon), but their initial transitions are not executed. The process in turn to be executed is the Main process. You can check this by viewing the process ready queue:
- Locate the button module View in the left part of the window, and click the Ready Q button. The first entry in the ready queue is Main, waiting to execute its start transition.
- If required, resize the Explorer UI window so that all button modules are visible. You may also reduce the width of the text area. In the exercises to come, you will have a number of windows open at the same time.
Basics of an SDL Explorer
Before you start working with the explorer exercises, you should have an understanding about the basic concepts of the SDL Explorer.
- When examining an SDL system using the explorer, the SDL system is represented by a structure called a behavior tree. In this tree structure, a node represents a state of the complete SDL system. The collection of all such system states is known as the state space of the system.
- By moving around in the behavior tree, you can explore the behavior of the SDL system and examine each system state that is encountered. This is called state space exploration, and it can be performed either manually or automatically.
- The size and structure of the behavior tree is determined by a number of state space options in the explorer. These options affect the number of system states generated for a transition in an SDL process graph, and the number of possible branches from a state in the behavior tree.
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