Use Case Diagram (available in CORE Spectrum)

Use cases describe the functionality of a system from the user perspective. The use case diagram is a graphical representation of actors (humans), blocks (components), and use cases.



Use cases are effectively the names of MBSE threads, capturing concepts and context that should be translated into threads and the integrated system logic. They are often used as elicitation and discovery tools, helping to better understand the system under consideration and transition from requirements and operational context to behavioral threads. The conceptual modeling flow (in top-down design) begins with the requirements. From the requirements, you define the system boundary – physical and functional – and identify the context. From this context and the operational concept that drives it, use cases are identified. Use cases are then elaborated by functional threads which provide the insight needed to develop the integrated logic. A view of how use cases fit into the greater language of MBSE is shown below.



Note that this is not the only flow nor is it the prescribed flow. For example, use cases can be tied to requirements. They can also exist free-floating. However, the conceptual flow places use cases into the overall context of the MBSE model. They serve to make the development of threads more disciplined, explicit, and rich. At any layer of development, you can identify the threads that influenced the development of the integrated logic by

  1. Starting with the component’s root function
  2. Getting the component that performs the function
  3. Getting the use cases that describe the component
  4. Getting the threads that elaborate the use case


For the use case diagram


The use case diagram is a free-form diagram. CORE defaults to specific layout behaviors, but you are free to rearrange content within the bounds of certain constraints:



A good reference for further information on use case diagrams is chapter 12 of A Practical Guide to SysML: The Systems Modeling Language by Sanford Friedenthal, Alan Moore, and Rick Steiner (2012).

Diagram Options

In addition to the classic diagram options, the use case diagram settings include:

Diagram Palette

The constructs and key entities tabs allow you to quickly develop your use case model, while the all entities tab enables you to relate your use case model to the remainder of your system definition.

Diagram Menu Commands

Tips and Tricks