RUP 4+1 View

A Typical Set of Architectural Views 

Architecture is represented by a number of different architectural views, which in their essence are extracts illustrating the "architecturally significant" elements of the models. In the RUP, you start from a typical set of views, called the "4+1 view model". It is composed of:

• The  Use-Case View, which contains use cases and scenarios that encompasses architecturally significant behavior, classes, or technical risks. It is a subset of the use-case model.
• The Logical View, which contains the most important design classes and their organization into packages and subsystems, and the organization of these packages and subsystems into layers. It contains also some use case realizations. It is a subset of the design model.
• The Implementation View, which contains an overview of the implementation model and its organization in terms of modules into packages and layers. The allocation of packages and classes (from the Logical View) to the packages and modules of the Implementation View is also described. It is a subset of the implementation model.
• The Process View, which contains the description of the tasks (process and threads) involved, their interactions and configurations, and the allocation of design objects and classes to tasks. This view need only be used if the system has a significant degree of concurrency. In RUP, it is a subset of the design model.
• The Deployment View, which contains the description of the various physical nodes for the most typical platform configurations, and the allocation of tasks (from the Process View) to the physical nodes. This view need only be used if the system is distributed. It is a subset of the deployment model.

The architectural views are documented in a Software Architecture Document. You can envision additional views to express different special concerns: user-interface view, security view, data view, and so on. For simple systems, you may omit some of the views contained in the 4+1 view model.