How should SysML be applied to an MBSE project? How is SysML commonly abused?

As SysML emerges as the de facto standard for Model-Based Systems Engineering (MBSE) approaches there are three usage modes of progressive rigor in which it is being applied:
  • SysML-as-Pretty-Pictures: This is the most informal and least rigorous SysML usage mode. Unfortunately, it is also the most common way that SysML is abused. In SysML-as-Pretty-Pictures mode SysML notation is used in lieu of ad hoc modeling notation (e.g., Visio or PowerPoint drawings), but relatively little attention is paid to SysML wellformedness and its underlying simulatable semantics. Consequently, the SysML models generated in SysML-as-Pretty-Pictures model are rarely capable of driving dynamic simulations or precisely specifying system architecture blueprints.
  • SysML-as-System-Simulation: This SysML usage mode is a significant improvement over SysML-as-Pretty-Pictures mode, since it emphasizes the simulation of system dynamic behavior and system parametric constraints. In SysML-as-System-Simulation mode at least some of SysML behavioral diagrams (Activity, Sequence, State Machine diagrams) are exercised by a simulation engine, and some of the Parametric diagram constraints are exercised by a constraint propagation engine (MATLAB/Simulink, OpenModelica, SysML tool proprietary plugin, etc.).
  • SysML-as-System-Architecture-Blueprint: This SysML usage mode is a substantive improvement over SysML-as-System-Simulation mode, since it stresses the use of SysML to precisely specify a System Architecture Model that serves as system architecture "truth", and which satisfies the 5 C's (Correct, Complete, Clear, Concise, and Consistent). This is the most advanced SysML mode, and since it typically also includes simulatable behavioral and Parametric diagrams, it should be considered an evolution of the SysML-as-System-Simulation mode.

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