4+1 Views Model

4+1 is a view model designed by Philippe Kruchten for describing the architecture of software-intensive systems, based on the use of multiple, concurrent views. The views are used to describe the system in the viewpoint of different stakeholders, such as end-users, developers and project managers. The four views of the model are logical, development, process and physical view. In addition selected use cases or scenarios are utilized to illustrate the architecture serving as the 'plus one' view.

The views are -
• Logical view : The logical view is concerned with the functionality that the system provides to end-users. UML Diagrams to represent logical view include Class Diagram, Sequence diagram.
• Development/Implementation view : The development view illustrates a system from a programmers perspective and is concerned with software management. E.g Package diagram
• Process view : The process model deals with the dynamic aspect of the system, explains the system processes and how they communicate, and focuses on the runtime behavior of the system. E.g Activity Diagram
• Physical or Deployment view : The physical view depicts the system from a system engineer's point-of-view. It is concerned with the topology of software components on the physical layer, as well as communication between these components. E.g Deployment diagram
• Use case View : It is from the end user’s perspective. It details the functional requirements, the use cases and the users of the system. It overlaps with every other perspective in the system

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