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Scenario

The scenario is the blueprint of a process. It models a workflow as a fine-state machine. Within the scenario, we define all possible states, the state transitions and actions that trigger them, and the actors participating in the process.

The scenario models a process as a fine-state machine. The actors are persons, organizations, or systems that can participate in the process by performing actions. Which actions can be performed depends on the current state of the process. By executing an action, the process can transition to a different state.

{% hint style="info" %} The scenario may be defined in YAML or JSON. {% endhint %}

Schema

https://schemas.letsflow.io/v1.0/scenario

Properties

id

UUID

The scenario ID is generated based on the sha256 hash of JSON representation. Modifying a scenario will result in a different id.

{% hint style="warning" %} The engine automatically sets this field. You may omit it from your YAML or JSON file.

If you do need to set this manually, use the uuid() function from the core library to generate the correct ID. Using a different UUID may lead to unexpected results. {% endhint %}

name

string

A consistent name for the scenario. Scenarios can be referenced by name to get different versions. Each version will have a unique ID.

version

string

A semantic version of the scenario. Used in combination with the name.

title

string

A short description of the workflow. This is copied to the process during instantiation.

description

string

A short description of the workflow.

tags

array of strings

Tags can be used to filter a list of scenarios. Scenario tags are copied to the process, to be used to filter a list of processes.

actors

map of actor schemas

Actors that can participate in the process. The actor schema defines the properties of each actor.

{% content-ref url="actor.md" %} actor.md {% endcontent-ref %}

{% hint style="info" %} If the actors property is omitted, the process will have a single actor named actor with only the default properties. {% endhint %}

actions

map of actions

Actions can be implicitly defined through state transitions. However, to extend their functionality—such as adding update instructions, conditions, or properties for frontend integration—they must be explicitly defined.

{% content-ref url="action/" %} action {% endcontent-ref %}

states

map of states (required)

The scenario models a workflow as a finite state machine, which is comprised of states and state transitions. A scenario must at least define the initial state.

{% content-ref url="state/" %} state {% endcontent-ref %}

vars

map of schemas

Each schema defines a variable that is available in the process. The key of the map is used as the variable name.

result

schema

The result defines the schema for a special variable that represents the process's output. While primarily intended as the final result, this variable can be built up and used throughout the process.

Additional properties

You may add additional properties to the scenario. These are ignored by the core library and workflow engine.

The properties may have meaning for your application. For example; you can add a ui property for options for your front-end components.

ui:
  view: stepper
  adminControls: true

Additional properties can also be referenced in data functions when running the process. An example of using a custom messages property in the scenario:

notify:
  service: email
  message:
    recipient: !ref actors.client
    subject: Welcome to Acme
    body: !ref scenario.messages.introduction

{% hint style="warning" %} Do not use additional properties for filtering. Use the tags instead. {% endhint %}