Petri Net assignment

General Information

• The due date is Monday 24 October 2005, before 23:55.
  
  
• Submissions must be done via WebCT. Beware that WebCT's clock may differ slightly from yours. As described on the Assignments page, all results must be uploaded to WebCT and accessible from links in the index.html file. There is no need to upload AToM3.
  
  
• The assignment must be made in groups of maximum 2 people. It is understood that all partners will understand the complete assignment (and will be able to answer questions about it). Clearly identify who did what.
  
  
• Grading will be done based on correctness and completeness of the solution. Do not forget to document your requirements, assumptions, design, implementation and modelling and simulation results in detail !
  
  
• Extensions, if given, will involve extending not only the alotted time, but also the assignment !
  
  

The assignment: Petri Net modelling, simulation and analysis of a simple traffic system (using AToM³)

1. [6%] Modelling a simplified traffic intersection + analysis: The system depicted below is a four-direction (North, East, South and West) traffic intersection. Each direction has two lanes, i.e. an entrance and an exit. There are some constraints about the system as follows:
   1. At most one car is allowed to be present at the center of the intersection at any moment;
   2. No U-turns are allowed, e.g. a car entering from North is not allowed to exit to the North;
   3. The number of cars to enter the intersection from any direction can be infinite;
   4. After a car enters the intersection, the direction in which it exits is determined randomly.

   (1) [4%] Using AToM³, build and document a Petri Net model of the behaviour of this system. Documentation must describe how the different constraints given above were addressed. Include an image of the model in your solution.

   (2) [2%] Build the coverability graph for this Petri Net and draw some conclusions, including what is conserved in the system.

2. [4%] Modelling a simplified traffic roundabout (traffic circle) + analysis: The roundabout depicted below is very similar to the intersection. It has four directions (North, East, Southa and West) and each one has two lanes: an entrance and an exit. However, there are four arcs at the center of the roundabout. There are some constraints about the system as follows:
   1. At most one car is allowed to be present in each arc of the roundabout at any moment;
   2. U-turns or circling are allowed, e.g. a car entering from the North may exit to the North;
   3. The number of cars to enter the roundabout from any direction can be infinite;
   4. After a car enters the roundabout, the direction in which it exits is determined randomly.

   (1) [3%] Using AToM³, build and document a Petri Net model of the behaviour of this system. Documentation must describe how you've addressed the different constraints given above. Include an image of this model in your solution.

   (2) [1%] Build the coverability tree for this Petri Net and draw some conclusions, e.g. what is conserved in the system.

Constructing Petri Net models in AToM³

Download atom3.tar.gz archive. Note how this is a new archive (not the same as the one for the first assignment) by which you can do conservation analysis automatically on the generated coverability graph.