Which type of diagram is NOT classified under SysML?

The classification of diagrams in Systems Modeling Language (SysML) includes several categories, each serving specific purposes in systems engineering. Among these, block definition diagrams, parametric diagrams, and behavior diagrams are integral parts of SysML.

Block definition diagrams are used to represent the system's structure and define the types of blocks and their relationships. This helps in visualizing how components interact within the system architecture.

Parametric diagrams focus on capturing constraints and relationships among system parameters, crucial for performance and quantitative analysis. They allow for detailed modeling of the properties and functionalities of complex systems.

Behavior diagrams provide insights into the dynamic aspects of the system, illustrating how the system behaves over time, including use case diagrams and state machine diagrams.

In contrast, activity diagrams, although important in system design and process modeling, are not classified specifically as SysML diagrams. They are more closely associated with Unified Modeling Language (UML), which has different objectives and a broader application beyond SysML's specific context in systems engineering. Therefore, identifying activity diagrams as not being classified under SysML reflects a distinction between the two modeling languages used in systems engineering contexts.