11. MVP Domain Processes

Overview

This document describes the main process flows in the Retrofit Workflow Context.

Wagon Flow Process

Train Arrival
    ↓
Arrival Coordinator (classify wagons)
    ↓
Collection Coordinator (form batches)
    ↓
Workshop Coordinator (retrofit)
    ↓
Parking Coordinator (to parking)
    ↓
Complete

Detailed Process Flows

1. Train Arrival Process

Coordinator: ArrivalCoordinator

Steps: 1. Receive TrainArrivedEvent from External Trains 2. Classify each wagon on intake — the eligibility gate: loaded wagons and wagons that don't need a retrofit (e.g. already-DAC) are rejected here (REJECTED_LOADED / REJECTED_NO_RETROFIT_NEEDED) and never become wagon entities 3. For eligible wagons, select a collection track (via the Railway Infrastructure track-selection service) 4. Place wagons on the collection track — if no track has room, the wagon is rejected on capacity (NO_COLLECTION_TRACK / COLLECTION_TRACK_FULL) 5. Hand placed wagons to the collection queue

Note: the eligibility rejection (loaded / no-retrofit) happens at classification (step 2), before track placement. The only rejection at placement (step 4) is capacity (track-full).

Domain Services Used: - Wagon eligibility / classification (WagonEligibilityService) — the accept/reject gate at arrival - Track selection (TrackSelectionService)

2. Collection Process

Coordinator: CollectionCoordinator

Steps: 1. Wait for wagons in collection queue 2. Collect batch (up to batch_size) 3. Allocate locomotive 4. Form rake (couple wagons) 5. Form train (locomotive + rake) 6. Transport to retrofit track 7. Decouple wagons 8. Release locomotive

Domain Services Used: - BatchFormationService - RakeFormationService - TrainFormationService - RouteService

3. Workshop Process

Coordinator: WorkshopCoordinator

Steps: 1. Wait for batch on retrofit track 2. Select workshop with capacity 3. Allocate locomotive 4. Transport batch to workshop track 5. Decouple wagons sequentially 6. Assign each wagon to retrofit station 7. Execute retrofit (parallel) 8. Couple completed wagons 9. Transport to retrofitted track 10. Release locomotive

Domain Services Used: - WorkshopSchedulingService - CouplingService - RouteService

4. Parking Process

Coordinator: ParkingCoordinator

Steps: 1. Wait for wagons on retrofitted track 2. Form batch 3. Allocate locomotive 4. Transport to parking track 5. Place wagons 6. Release locomotive

Domain Services Used: - BatchFormationService - RouteService

State Machines

Wagon State Machine

The WagonStatus enum (contexts/retrofit_workflow/domain/entities/wagon.py) defines the states:

ARRIVED → CLASSIFIED → READY_FOR_RETROFIT → RETROFITTING → RETROFITTED → PARKED

Wagons that are loaded or do not need a retrofit are rejected during classification (recorded as a REJECTED event in the wagon journey).

Timing

Timing parameters are defined in ProcessTimes (contexts/configuration/domain/models/process_times.py):

• wagon_retrofit_time
• screw_coupling_time / screw_decoupling_time
• dac_coupling_time / dac_decoupling_time
• train_to_hump_delay, wagon_hump_interval

Resource Constraints

• Locomotives: Limited pool, allocated on demand
• Tracks: Capacity based on length and fill factor
• Workshops: Limited retrofit stations

Error Handling

• Insufficient capacity: Wagon waits in queue
• No locomotive available: Process blocks until available
• Invalid route: Simulation error

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