We complement our specification of the vending machine given in Section 1.4 to make it more realistic. We include the following into the model:
External places to the vending machine are the three places READY, Coin inserted, and Service man at VM (SM). There are three sub-nets, Coin handling, Dispensing, and Replenishment.
- Insertion of coin
- Coin may be accepted or rejected
- Box for accepted coins
- READY true only if there are goods to dispense
- Replenishment takes place when service man arrives
- The service man also empties the coin box
The net Coin handling has the external places READY, Coin inserted (CI), Coin box (CB), and Ready to dispense (RD) as external places.
The net Dispensing has the external places Ready to dispense, READY, Goods storage (GS), and Goods free slots (GF).
The net Replenishment has the external places Goods storage, Goods free slots, Coin box, and Service man at VM.
The crude model in letter art is given below: (drawings)
_______________________________________________ |Vending machine _________ | | |Dispen- |-----(5) GS | ,------------------------|sing | ^ | v | _________ |_________\ _|__________ | (•)-----|---|Coin | ^ \ |Replenish- | | READY | |handling | RD | v |ment | | | | |---->( ) GF ( )--| | | ( )-------->| | | | | CI | |_________|------->( )--------| | | | CB | | | | |___________| | |________________________________________|______| | ( ) SM