Page 109 - Getting the Picture Modeling and Simulation in Secondary Computer Science Education

Assessment of Modeling and Simulation
transition from the state begin to the state ready occurs, and that is the action show up. The NetLogo go procedure then runs repeatedly until the program stops and according to our convention, every time it runs, exactly one transitions originating from the ready state takes place, and when the procedure has finished one run the vehicle is back in the ready state unless it reached the gone state. This is not to say that during one run of the go procedure an agent may engage in one state transition only: rather, it means that one full cycle of actions emanating from the ready state takes place. For each transition, there might be conditions that need to be met in order for the transition to occur, and properties could be updated. For example, move only occurs if the position in front of the vehicle is free and then its property current position is updated. State transitions could be synchronized with each other as well, such as in the famous Wolf Sheep Predation model: a wolf can eat only if one of the sheep simultaneously dies (Wilensky, 1997).
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Wait
Guard: the position in front is not free
Ready Leave Gone Guard:
current position == target position
Move
Guard: the position in front is free Update: update current position
Begin
Show up
Figure 4: State diagram for vehicle
Finally, there is an additional textual description of a number of relevant aspects of the model. It mentions that a roundabout itself can be modeled as well while that is not strictly necessary since the vehicles know where they are through their current position property; that the show up action does not necessarily require a vehicle to stop in front of an empty roundabout, and that it is up to the modeler to decide on design details such as how far can a vehicle move during one run of the go procedure.
As elaborated in the section on assignment (section 5.3.1), the evidence the students provide about their models is twofold: the textual descriptions they formulate when designing the model and the implemented model, i.e. NetLogo program code (Müller et al., 2014). Our description format helps educators to distil the relevant aspects of the models from the descriptions and code students turn in and to employ the rubrics based on the SOLO categories.
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