What is a parametric diagram primarily used for in SysML?

A parametric diagram in SysML is primarily utilized to express system performance and constraints. This type of diagram is particularly focused on capturing the relationships among system parameters, which can be quantities or variables that are essential for evaluating the system’s behavior and performance. By defining how different parameters relate to one another through equations, inequalities, or other mathematical representations, the parametric diagram allows engineers to analyze and validate system performance as it evolves, ensuring that it meets specified criteria and constraints.

This diagram supports system design and analysis by linking performance attributes to their underlying variables, enabling effective trade-offs and optimizations during the engineering process. By understanding how changes in one parameter affect others, systems engineers can make informed decisions that enhance the system's overall functionality and compliance with requirements.

While the other choices mention different diagram purposes, they do not align with the primary function of a parametric diagram. Geometric shapes pertain more to block diagrams, user interactions are better represented in use case diagrams, and system structure is typically outlined in block definition diagrams or internal block diagrams.