The emphasis of the Webel recipe for modelling Mathematica code in Systems Modeling Language v1 (SysML®) is on capturing the logic flow (using Activity Diagrams), equation networks (using SysML Parametric Diagrams and/or SysML Activity Diagrams), and main data structures (using SysML Blocks) of the Mathematica code. It is not intended that every single Mathematica code construct be replicated in SysML!
In many cases networks of equations can be accurately encapsulated as SysML Parametric Diagrams and then executed in Magic Model Analyst® (Cameo Simulation Toolkit®), but the main aim is to represent the dependencies of parameters graphically, and this can be of enormous benefit. Indeed, creating a SysML Parametric Diagram first can be an excellent way to plan your Mathematica code efficiently.
It is however much harder to create SysML Activity Diagrams that can be executed to mimic the execution of Mathematica code. The main benefit is to be found in creating SysML Activity Diagrams that capture the function logic, the flow of information between functions, and the parameter dependencies. This can be very useful for planning and recording refactoring of Mathematica code, and serves as excellent documentation of a Mathematica code system.