Migration coexistence

Old and new domains side by side with @deprecated / @migration_target.

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System view

Source

migration/system.krs

// Demonstrates: @deprecated, @migration_target, @experimental annotations
// Also intentionally triggers a domain drift WARNING:
//   domain "Order" appears in both LegacyMonolith and OrderService within the same system.
//
// This pattern models a system mid-migration where the same business domain
// is temporarily owned by two services. The warning signals that migration is incomplete.

system ECommercePlatform {
  label "EC Platform (migrating)"

  user Customer [human] {
    label "Buyer"
    role "General user who purchases products"
  }

  // @deprecated: scheduled for decommission after migration completes
  service LegacyMonolith @deprecated {
    label "Legacy Monolith"
    description "The old monolithic application. Scheduled for decommission in 2026 Q3"

    domain Order {
      label "Orders (old)"
      usecase PlaceOrder { label "Accept an order" }
      usecase QueryOrder { label "Look up order status" }
    }

    domain Catalog {
      label "Product Catalog (old)"
      usecase SearchProducts { label "Search products" }
    }
  }

  // @migration_target: the new service that will take over from LegacyMonolith
  service OrderService @migration_target {
    label "Order Service"
    description "Microservice carved out of the orders domain"

    // Same domain id "Order" as in LegacyMonolith → triggers domain drift warning
    domain Order {
      label "Orders (new)"
      usecase PlaceOrder { label "Accept an order" }
      usecase CancelOrder { label "Cancel an order" }
      usecase QueryOrder { label "Look up order status" }
    }
  }

  // @experimental: new service, API not yet stable
  service CatalogService @experimental {
    label "Catalog Service"
    description "Microservice carved out of the product catalog. API may change"

    domain Catalog {
      label "Product Catalog (new)"
      usecase SearchProducts { label "Search products" }
      usecase UpdateProduct { label "Update product details" }
    }
  }

  service Payment {
    label "Payment"
    description "Credit card payment processing"
  }

  Customer        ->  LegacyMonolith  "Purchase (old flow)"
  Customer        ->  OrderService    "Purchase (new flow)"
  LegacyMonolith  ->  Payment         "Process payments"
  OrderService    ->  Payment         "Process payments"
  OrderService    ->  CatalogService  "Fetch product details"
}