Examples

Appointments & weather

All four workflow patterns in an appointments-and-weather domain.

state_changestate_viewautomationtranslation

The rendered canvas

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The source

Source file: examples/appointment-weather-patterns.em.hcl.

# Appointment scheduling with state change, state view, automation, and translation workflows. actor "scheduler" { title = "Scheduler" auth_required = true } actor "calendar_user" { title = "Calendar user" auth_required = true } system "weather_provider" { title = "Weather provider" external = true } bounded_context "appointments" { title = "Appointments" aggregate "appointment" { } field_type "appointment_id" { type = "UUID" id_attribute = true } field_type "starts_at" { type = "DateTime" } event "appointment_added" { title = "Appointment Added" aggregate = aggregate.appointment field "appointment_id" { type = field_type.appointment_id } field "starts_at" { type = field_type.starts_at } } } bounded_context "weather" { title = "Weather" aggregate "weather_forecast" { } field_type "forecast" { type = "String" } field_type "changed_at" { type = "DateTime" } event "weather_predicted_for_appointment" { title = "Weather predicted for appointment" aggregate = aggregate.weather_forecast field "appointment_id" { type = field_type.appointments.appointment_id } field "forecast" { type = field_type.forecast } } event "updated_weather_prediction" { title = "Updated Weather Prediction" aggregate = aggregate.weather_forecast field "appointment_id" { type = field_type.appointments.appointment_id } field "forecast" { type = field_type.forecast } } } bounded_context "weather_provider" { title = "Weather Provider" owner = system.weather_provider external = true event "weather_forecast_changed" { title = "Weather Forecast Changed" field "appointment_id" { type = field_type.appointments.appointment_id } field "forecast" { type = field_type.weather.forecast } field "changed_at" { type = field_type.weather.changed_at } } } state_change "schedule_appointment" { title = "Schedule Appointment" screen "schedule_appointment_ui" { title = "UI" actor = actor.scheduler to = [command.add_appointment] } screen "post_appointment" { title = "POST /appointment" to = [command.add_appointment] } command "add_appointment" { title = "Add Appointment" aggregate = aggregate.appointments.appointment to = [event.appointments.appointment_added] field "appointment_id" { type = field_type.appointments.appointment_id } field "starts_at" { type = field_type.appointments.starts_at } } scenario "appointment_is_scheduled" { title = "Schedule an appointment" when { title = "Add Appointment" command = command.add_appointment field "appointment_id" { type = field_type.appointments.appointment_id } field "starts_at" { type = field_type.appointments.starts_at } } then { title = "Appointment Added" event = event.appointments.appointment_added field "appointment_id" { type = field_type.appointments.appointment_id } field "starts_at" { type = field_type.appointments.starts_at } } } } state_view "view_calendar" { title = "View Calendar" readmodel "calendar" { title = "Calendar" question = "Which appointments are on the calendar?" from = [event.appointments.appointment_added] to = [screen.calendar_ui, screen.get_calendar] field "appointment_id" { type = field_type.appointments.appointment_id } field "starts_at" { type = field_type.appointments.starts_at } } screen "calendar_ui" { title = "UI" actor = actor.calendar_user } screen "get_calendar" { title = "GET /calendar" } scenario "calendar_shows_scheduled_appointment" { title = "Show a scheduled appointment on the calendar" given { title = "Appointment Added" event = event.appointments.appointment_added field "appointment_id" { type = field_type.appointments.appointment_id } } then { title = "Calendar" readmodel = readmodel.calendar field "appointment_id" { type = field_type.appointments.appointment_id } field "starts_at" { type = field_type.appointments.starts_at } } } } automation "add_weather_forecast" { title = "Add Weather Forecast" readmodel "appointments_without_weather_forecast" { title = "Appointments without weather forecast" question = "Which appointments do not have a weather forecast?" from = [event.appointments.appointment_added] to = [processor.weather_processor] field "appointment_id" { type = field_type.appointments.appointment_id } field "starts_at" { type = field_type.appointments.starts_at } } processor "weather_processor" { title = "Weather Processor" to = [command.add_weather_forecast_command] } command "add_weather_forecast_command" { title = "Add Weather Forecast" aggregate = aggregate.weather.weather_forecast to = [event.weather.weather_predicted_for_appointment] field "appointment_id" { type = field_type.appointments.appointment_id } field "forecast" { type = field_type.weather.forecast } } scenario "forecast_is_added_for_new_appointment" { title = "Add a weather forecast for a scheduled appointment" given { title = "Appointment Added" event = event.appointments.appointment_added field "appointment_id" { type = field_type.appointments.appointment_id } field "starts_at" { type = field_type.appointments.starts_at } } given { title = "Appointments without weather forecast" readmodel = readmodel.appointments_without_weather_forecast } when { title = "Weather Processor" processor = processor.weather_processor } then { title = "Weather predicted for appointment" event = event.weather.weather_predicted_for_appointment field "appointment_id" { type = field_type.appointments.appointment_id } field "forecast" { type = field_type.weather.forecast } } } } translation "translate_weather_change" { title = "Translate Changed Weather" readmodel "changed_predictions" { title = "Changed Predictions" question = "Which external weather predictions changed?" from = [event.weather_provider.weather_forecast_changed] to = [processor.translator] field "appointment_id" { type = field_type.appointments.appointment_id } field "forecast" { type = field_type.weather.forecast } } processor "translator" { title = "Translator" to = [command.translate_changed_weather] } command "translate_changed_weather" { title = "Translate Changed Weather" aggregate = aggregate.weather.weather_forecast to = [event.weather.updated_weather_prediction] field "appointment_id" { type = field_type.appointments.appointment_id } field "forecast" { type = field_type.weather.forecast } } scenario "external_weather_change_is_translated" { title = "Translate a changed external weather forecast" given { title = "Weather Forecast Changed" event = event.weather_provider.weather_forecast_changed field "appointment_id" { type = field_type.appointments.appointment_id } field "forecast" { type = field_type.weather.forecast } } given { title = "Changed Predictions" readmodel = readmodel.changed_predictions } when { title = "Translator" processor = processor.translator } then { title = "Updated Weather Prediction" event = event.weather.updated_weather_prediction field "appointment_id" { type = field_type.appointments.appointment_id } field "forecast" { type = field_type.weather.forecast } } } }