Simulation Lifecycle Events

5 minute read

The following events control the lifecycle of the simulation. They govern the starting, initializing, pausing, resuming, and stopping of the simulation as well as the associated state transitions.

State Model

The simulation passes through the following states:

[START] → INITIALIZING → RUNNING ⇄ PAUSED → STOPPED

State transitions are triggered by command events and confirmed by simulation:state notification events.

Event Overview and Lifecycle

Event	Category	Type	Description
`start`	`simulation`	Command	Starts the simulation
`reset`	`simulation`	Command	Resets the simulation to its initial state
`initialize-world`	`simulation`	Command (internal)	Initializes the simulation world
`initialize`	`simulation`	Command	Requests all clients to initialize
`initialized`	`client`	Response	Confirms that a client has completed initialization
`state`	`simulation`	Notification	Informs about state changes
`pause`	`simulation`	Command	Pauses the simulation
`continue`	`simulation`	Command	Resumes a paused simulation
`stop`	`simulation`	Command	Stops the simulation

OPTIMIZER/VISUALIZATION          SIMULATION                   ALL CLIENTS
        |                            |                             |
        |--- simulation:start -----> |                             |
        |                            |-- simulation:state -------> |  (INITIALIZING)
        |                            |-- simulation:reset -------> |
        |                            |-- simulation:init-world (internal)
        |                            |-- simulation:initialize --> |
        |                            |                             |
        |                            |<-- client:initialized ----- |  (per client)
        |                            |<-- client:initialized ----- |
        |                            |                             |
        |                            |-- simulation:state -------> |  (RUNNING)
        |                            |                             |
        |--- simulation:pause -----> |                             |
        |                            |-- simulation:state -------> |  (PAUSED)
        |                            |                             |
        |--- simulation:continue --> |                             |
        |                            |-- simulation:state -------> |  (RUNNING)
        |                            |                             |
        |--- simulation:stop ------> |                             |
        |                            |-- simulation:state -------> |  (STOPPED)

Events in Detail

`simulation:start`

Starts the simulation. This event triggers the initialization process of the simulation.

Senders

OPTIMIZER,
VISUALIZATION

Receivers

SIMULATION

Data Fields

This event contains no data fields.

Example

{
  "category": "simulation",
  "name": "start",
  "data": {}
}

Flow after Triggering

The simulation receives simulation:start.
The simulation sends simulation:state with state: "INITIALIZING".
The simulation sends simulation:reset.
The simulation sends simulation:initialize-world internally.
The simulation sends simulation:initialize.
All clients respond with client:initialized.
Once all clients have confirmed, the simulation sends simulation:state with state: "RUNNING".

`simulation:state`

Informs all participants about a state change of the simulation. This event is sent exclusively by the simulation and serves as confirmation of a completed state transition.

Senders

SIMULATION

Receivers

OPTIMIZER,
SIMULATION,
VISUALIZATION

Data Fields

Field	Type	Required	Description
`state`	`string`	Yes	The new state of the simulation. Possible values: `INITIALIZING`, `RUNNING`, `PAUSED`, `STOPPED`

Example

{
  "category": "simulation",
  "name": "state",
  "data": {
    "state": "INITIALIZING"
  }
}

Valid State Transitions

Previous State	New State	Triggering Event
`STOPPED`	`INITIALIZING`	`simulation:start`
`INITIALIZING`	`RUNNING`	All `client:initialized` received
`RUNNING`	`PAUSED`	`simulation:pause`
`PAUSED`	`RUNNING`	`simulation:continue`
`RUNNING`	`STOPPED`	`simulation:stop`
`PAUSED`	`STOPPED`	`simulation:stop`

`simulation:reset`

Resets the simulation to its initial state. This event is sent by the simulation during the initialization process and signals all participants to reset their internal state.

Senders

SIMULATION

Receivers

OPTIMIZER
SIMULATION
VISUALIZATION

Data Fields

This event contains no data fields.

Example

{
  "category": "simulation",
  "name": "reset",
  "data": {}
}

`simulation:initialize-world`

Initializes the simulation world. This is a simulation-internal event and is processed exclusively within the simulation. It is used to build the world structure (e.g., terrain, objects, entities) before the clients are initialized.

Senders

SIMULATION

Receivers

SIMULATION

Data Fields

This event contains no data fields.

Example

{
  "category": "simulation",
  "name": "initialize-world",
  "data": {}
}

`simulation:initialize`

Requests all clients to initialize themselves. This event is sent after the simulation world has been built. Each receiving client must respond with a client:initialized event upon completion of its initialization.

Senders

SIMULATION

Receivers

OPTIMIZER
SIMULATION
VISUALIZATION

Data Fields

This event contains no data fields.

Example

{
  "category": "simulation",
  "name": "initialize",
  "data": {}
}

Expected Receiver Behaviour

Each receiver must send a client:initialized event to the simulation after successful initialization. The simulation waits for confirmation from all clients before transitioning to the RUNNING state.

`client:initialized`

Confirms that a client has completed its initialization. This event is sent in response to simulation:initialize. The simulation waits for a client:initialized event from each registered client before transitioning to the RUNNING state.

Senders

OPTIMIZER
SIMULATION
VISUALIZATION

Receivers

SIMULATION

Data Fields

This event contains no data fields.

Example

{
  "category": "client",
  "name": "initialized",
  "data": {}
}

`simulation:pause`

Pauses the running simulation. The simulation transitions to the PAUSED state and confirms this by sending a simulation:state event.

Senders

VISUALIZATION

Receivers

OPTIMIZER
SIMULATION
VISUALIZATION

Data Fields

This event contains no data fields.

Example

{
  "category": "simulation",
  "name": "pause",
  "data": {}
}

Flow after Triggering

The visualization sends simulation:pause.
The simulation receives the event and transitions to the PAUSED state.
The simulation sends simulation:state with state: "PAUSED".

`simulation:continue`

Resumes a paused simulation. The simulation transitions back to the RUNNING state and confirms this by sending a simulation:state event.

Senders

VISUALIZATION

Receivers

OPTIMIZER
SIMULATION
VISUALIZATION

Data Fields

This event contains no data fields.

Example

{
  "category": "simulation",
  "name": "continue",
  "data": {}
}

Flow after Triggering

The visualization sends simulation:continue.
The simulation receives the event and transitions back to the RUNNING state.
The simulation sends simulation:state with state: "RUNNING".

`simulation:stop`

Stops the simulation. The simulation is terminated and transitions to the STOPPED state.

Senders

OPTIMIZER
VISUALIZATION

####Receivers

OPTIMIZER
SIMULATION
VISUALIZATION

Data Fields

This event contains no data fields.

Example

{
  "category": "simulation",
  "name": "stop",
  "data": {}
}

Flow after Triggering

The optimizer or the visualization sends simulation:stop.
The simulation receives the event and transitions to the STOPPED state.
The simulation sends simulation:state with state: "STOPPED".

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