TASK 1 Petri net system

Develop a Petri net system that captures all the processes in the scenario description. As this model will be used as a basis for implementing an information system to support Middlemans Purchase Order process, it must reflect the scenario as closely as possible. Ensure that your model is free of syntactic errors. Most importantly, the model must be semantically valid and complete as per the scenario description, i.e. every execution sequence of your Petri net system must reflect a valid sequence of steps from the scenario description and every sequence of steps from the scenario description must be reflected in some execution sequence of your Petri net system.

SCENARIO

Middleman Suppliers wishes to automate its purchase order process. The current purchase order process is described below:

1. a) When the quantity on hand of a stock item falls below re-order level, a Purchase Order (PO) for the stock item is raised. Each stock item in Middlemans inventory has a Preferred Supplier recorded and the Preferred Suppliers delivery timeframe (e.g. five days after receipt of PO). When raising a PO, the Purchasing Officer first contacts the Preferred Supplier to check on availability, current price.
2. b) If the stock item is available and at a price acceptable to the Purchasing Officer, the PO is completed and sent to the Preferred Supplier.
3. c) If the ordered goods have not arrived at Middlemans after the delivery timeframe (i.e. the goods are late in arriving at Middlemans), the Purchasing Officer contacts the Preferred Supplier for a revised delivery date. If the delivery date is too far into the future, the Purchasing Officer may cancel the PO.
4. d) On receipt of the ordered goods, the suppliers invoice and delivered goods are checked against the PO to ensure the correct quantity has been delivered and that none of the items are damaged.
5. e) If the invoice and delivered goods match the PO, the goods are put away in the warehouse, the Quantity on Hand value of the stock item is updated in the system, and payment of the invoice is approved.
6. f) Once all these steps are completed, payment is made, and the process completes.
7. g) If the invoice and goods received do not match the PO, the Supplier is advised. If the quantity delivered in acceptable condition is less than the PO quantity, the supplier will provide a credit note for the shortfall and the difference between quantity delivered (undamaged) and PO quantity is used to initiate a Backorder. The accepted goods are put away, the Quantity on Hand is updated, payment for this portion is approved and made. If the quantity delivered exceeds the PO quantity, Middlemans will initiate a Return process for the excess, put the goods away, update Quantity on Hand, approve payment for the PO quantity and make payment to the supplier.
8. h) If a new item is to be added to Middlemans inventory, the Purchasing Officer first conducts a search for a potential supplier. If a supplier is found, the item is entered into the inventory and the supplier is entered as the Preferred Supplier. The PO process continues from step b) above.
9. i) If no Preferred Supplier, for an existing or new stock item can be found, the process ends with no PO being raised.