State transducer visualization tool

This online tool consists of one window where the state transducer specification is to be entered; a button which when click triggers the display the graph visualization for the transducer, and last a window holding the graph visualization itself.

The format for the specification is immediately derived from the transducer format FSM_Dek from our state machine library with the following rules :

• we only keep the properties states and transitions from FSM_Def
• functions (e.g. predicates and actions) are replaced by their name

We thus end like with a JSON-like format.

The initial window starts with the example specification for a CD player :

  {
    "states": ["nok", [
      ["no_cd_loaded", [
        "cd_drawer_closed",
        "cd_drawer_open",
        "closing_cd_drawer"
      ]],
      ["cd_loaded", [
        ["cd_loaded_group", [
          ["cd_paused_group", [
            "time_and_track_fields_not_blank",
            "time_and_track_fields_blank"
          ]],
          "cd_playing",
          "cd_stopped"
        ]],
        "stepping_forwards",
        "stepping_backwards"
      ]]
    ]],
    "transitions": [
      { "from": "nok", "to": "no_cd_loaded", "event": "init", "action": "fsm_initialize_model" },
      { "from": "no_cd_loaded", "to": "cd_drawer_closed", "event": "init", "action": "identity" },
      { "from": "cd_drawer_closed", "to": "cd_drawer_open", "event": "EJECT", "action": "open_drawer" },
      { "from": "cd_drawer_open", "to": "closing_cd_drawer", "event": "EJECT", "action": "close_drawer" },
      {
        "from": "closing_cd_drawer", "guards": [
          { "predicate": "is_not_cd_in_drawer", "to": "cd_drawer_closed", "action": "identity" },
          { "predicate": "is_cd_in_drawer", "to": "cd_loaded", "action": "identity" }
        ]
      },
      { "from": "cd_loaded", "to": "cd_loaded_group", "event": "init", "action": "identity" },
      { "from": "cd_playing", "to": "cd_paused_group", "event": "PAUSE", "action": "pause_playing_cd" },
      { "from": "cd_paused_group", "to": "cd_playing", "event": "PAUSE", "action": "resume_paused_cd" },
      { "from": "cd_paused_group", "to": "cd_playing", "event": "PLAY", "action": "resume_paused_cd" },
      { "from": "cd_paused_group", "to": "time_and_track_fields_not_blank", "event": "init", "action": "identity" },
      {
        "from": "time_and_track_fields_not_blank",
        "to": "time_and_track_fields_blank",
        "event": "TIMER_EXPIRED",
        "action": "create_pause_timer"
      },
      {
        "from": "time_and_track_fields_blank",
        "to": "time_and_track_fields_not_blank",
        "event": "TIMER_EXPIRED",
        "action": "create_pause_timer"
      },
      { "from": "cd_paused_group", "to": "cd_stopped", "event": "STOP", "action": "stop" },
      { "from": "cd_stopped", "to": "cd_playing", "event": "PLAY", "action": "play" },
      { "from": "cd_playing", "to": "cd_stopped", "event": "STOP", "action": "stop" },
      { "from": "cd_loaded_group", "to": "cd_stopped", "event": "init", "action": "stop" },
      {
        "from": "cd_loaded_group", "event": "NEXT_TRACK", "guards": [
          { "predicate": "is_last_track", "to": "cd_stopped", "action": "stop" },
          { "predicate": "is_not_last_track", "to": "history.cd_loaded_group", "action": "go_next_track" }
        ]
      },
      {
        "from": "cd_loaded_group", "event": "PREVIOUS_TRACK", "guards": [
          { "predicate": "is_track_gt_1", "to": "history.cd_loaded_group", "action": "go_previous_track" },
          { "predicate": "is_track_eq_1", "to": "history.cd_loaded_group", "action": "go_track_1" }
        ]
      },
      { "from": "cd_loaded", "to": "cd_drawer_open", "event": "EJECT", "action": "eject" },
      {
        "from": "stepping_forwards", "event": "TIMER_EXPIRED", "guards": [
          { "predicate": "is_not_end_of_cd", "to": "stepping_forwards", "action": "go_forward_1_s" },
          { "predicate": "is_end_of_cd", "to": "cd_stopped", "action": "stop" }
        ]
      },
      { "from": "stepping_forwards", "to": "history.cd_loaded_group", "event": "FORWARD_UP", "action": "stop_forward_timer" },
      { "from": "cd_loaded_group", "to": "stepping_forwards", "event": "FORWARD_DOWN", "action": "go_forward_1_s" },
      { "from": "stepping_backwards", "to": "stepping_backwards", "event": "TIMER_EXPIRED", "action": "go_backward_1_s" },
      { "from": "stepping_backwards", "to": "history.cd_loaded_group", "event": "REVERSE_UP", "action": "stop_backward_timer" },
      { "from": "cd_loaded_group", "to": "stepping_backwards", "event": "REVERSE_DOWN", "action": "go_backward_1_s" }
    ]
  }

You can modify directly the specifications manually, and click the generate graph buttons when you are done. At this point of time, there is nothing done in term of error management. This means that if your modification of the graph is incorrect, the display will not be updated, with no visible error message displayed (there might be some indications on what went wrong in the console though).

Adjusting

Dagre does some nice visualizations. However they often have to be manually adjusted. We use cytoscape as a graph visualization library as it allows to adjust the graph manually.

For example, here is the automatic visualization generated by the Dagre layout engine for the CD player specification :

Here is the result of a manual adjustment, to have less edge-crossing and more readable labels :

For information, PlantUML not so good for visualizing complex state machines. However it is still useful as the generated SVG can be customized at will.

In conclusion, such an automatic visualization is useful. Even though it has to be improved manually, a good part of the layout is already done. It will be interesting in a future version to investigate how other engines display complx compound graphs.

Quick start

• npm run parcel
• then open a web browser at the indicated address (should be displayed as a link in your terminal after running parcel)

Visualization parameters

Compound state entry transitions are represented by 2-segments line. History states have H as state name. Self-loop are forced to Bezier curves. Other parameters could be used. To modify them, see the code.

Documentation

That README.md essentially. For details about the state transducer library, its motivation and format, please refer to the corresponding github directory.

Contributing

Anyone is welcome to contribute, however, if you decide to get involved, please take a moment to review the guidelines:

• Bug reports
• Feature requests
• Pull requests

License

The code is available under the MIT license.