4+1 View Model Taxonomy

4+1 Architectural View Model

Classification scheme based on Philippe Kruchten's 4+1 View Model (IEEE Software, 1995). Organizes architecture descriptions into four concurrent views (Logical, Process, Development, Physical) plus a unifying Scenarios view that validates and illustrates the others.

• Logical View (Design View)
  Addresses the functional requirements — what the system provides to end users. Describes the key abstractions (objects, classes, packages) and their relationships. Concerned with decomposition, encapsulation, and interface design.

  Scope Note: In UML: class diagrams, object diagrams, package diagrams. In ArchiMate: Application layer elements (ApplicationComponent, ApplicationService, ApplicationInterface, DataObject). In C4: Component diagrams.

  Example: Domain model, service interfaces, module decomposition

  https://meta.linked.archi/4plus1#LogicalView
• Process View (Concurrency View)
  Addresses non-functional requirements — concurrency, distribution, performance, scalability, fault tolerance. Describes the runtime behavior: processes, threads, synchronization, and communication mechanisms.

  Scope Note: In UML: activity diagrams, sequence diagrams, state machine diagrams. In ArchiMate: Triggering and Flow relationships, ApplicationProcess, ApplicationEvent. In BPMN: full process models with gateways and events.

  Example: Message flows between services, event-driven choreography, thread pools

  https://meta.linked.archi/4plus1#ProcessView
• Development View (Implementation View)
  Addresses the organization of the software in its development environment. Describes modules, packages, layers, subsystems, and their dependencies. Concerned with build structure, team allocation, and reuse.

  Scope Note: In UML: component diagrams, package diagrams. In C4: Container diagrams (deployable units and their technology choices). In Backstage: Component and System catalog entries with ownership.

  Example: Microservice boundaries, shared libraries, monorepo structure

  https://meta.linked.archi/4plus1#DevelopmentView
• Physical View (Deployment View)
  Addresses the mapping of software to hardware — topology, deployment, communication, and infrastructure. Describes nodes, networks, and the allocation of processes and components to physical or virtual resources.

  Scope Note: In UML: deployment diagrams. In ArchiMate: Technology layer (Node, Device, SystemSoftware, CommunicationNetwork) with Assignment relationships. In C4: Deployment diagrams.

  Example: Kubernetes cluster topology, cloud region layout, network zones

  https://meta.linked.archi/4plus1#PhysicalView
• Scenarios View (+1 View) (Use Case View)
  The unifying view — a set of key scenarios (use cases) that drive and validate the architecture. Each scenario traces through the other four views, showing how elements from the Logical, Process, Development, and Physical views collaborate to fulfill a user goal.

  Scope Note: In UML: use case diagrams, sequence diagrams showing end-to-end scenarios. In ArchiMate: motivation elements (Stakeholder, Goal, Requirement) linked to application and business elements. In C4: System Context diagrams showing user interactions.

  Example: User places an order — traces from UI through services, queues, database, to deployment

  https://meta.linked.archi/4plus1#ScenariosView