December 19, 2017


Axe in hand, I strode into the misty forest, looking for the perfect Christmas tree. As the slushy snow soaked into my shoes, I thought, “I should have modeled this first!”

In any project as critical as decorating the house for Christmas, Model-Based Systems Engineering has a lot to offer the serious practitioner. In capturing use cases, it is important to remember the Christmas tree lifecycle of acquisition, display and disposal. Figure 1 shows a partial list of these elements.

Figure 1 SysML Use Case Diagram, Christmas Tree project phases

The project director must pay particular attention to the many stakeholders: children, spouse, spouse’s parents, etc., who will provide the requirements. A list of these is provided in Figure 2. These may initially be recorded in a specialized requirements management tool, but should ultimately be brought into the SysML model using an MBSE platform such as Syndeia™, so that they may be connected to the rest of the system model.

Figure 2  Initial requirements for Christmas tree

In Figure 3, we demonstrate the value of this. The requirements (in green) from Figure 2 form a clear hierarchy and the trace connections to the use cases (in red) from Figure 1, heavily annotated with notes (in yellow), provide a remarkably clear picture of the Christmas tree in all its complexity.

Figure 3 Requirements diagram showing trace relationships between use cases and requirements.

Merry Christmas to all our friends and colleagues. May your holidays be happy, bright and fully validated!

SysML model – MagicDraw

Dirk Zwemer

Dr. Dirk Zwemer ( is President of Intercax LLC (Atlanta, GA), a supplier of MBE engineering software platforms like Syndeia and ParaMagic. He is an active teacher and consultant in the field and holds Level 4 Model Builder-Advanced certification as an OMG System Modeling Professional.