Data flow diagram and context diagram
Acme has a store in Carson. Customers come into the store and browse the catalog of products. Once they have located the product they would like to purchase, they can take the unique identification number each product has and enter it into the inventory devices on the shop floor. By entering the number, the system will be able to show the customer the details of the product, whether it required home delivery and how many are left in stock. If the customer wants to purchase the product, they fill in a slip of paper with the identification code and the desired quantity and queue for the check-out and give it to the sales assistant. At the check-out, the sales assistant will take the slip and input the identification number into the system via their keyboard. If it shows that there are still some of the products in stock, the customer will be asked for payment (cash, or credit card). Once the transaction is complete it is saved to the transaction file and the customer will be given a receipt which also shows what counter they should collect the product at and an approximation of how long they will be waiting. In the stock room as transactions occur, staffs are notified of the product and quantity and will search the stock room and bring the product to the counter for collection. They will input into the system that the order has been filled and that the customer can collect it (the product catalog will be amended for stock level); the overhead screen will indicate to the customer that they may collect their order and at which counter. The customer may then pick up the product and leave the store. Periodically, as products are purchased the stock will run out (stock levels will be checked) and will have to be reordered from the supplier. Acme uses a wide number of suppliers so they keep a list of their contact details and the products they supply. Acme records all details relating to orders in the product-order file, this can be used to verify incoming orders later. The supplier receives a batch order for products periodically which they will fill and notify Acme of the delivery time and cost.
The following is the context diagram.
(1) Decompose the context diagram into more detailed levels (at least a level 0 diagram. But if you think you need to further decompose it to level 1 diagram, it is fine too).
(2) For each of the primitive DFD processes you have in (1), write the process descriptions using Structured English or pseudo code.
Acme: POS System
- Customer input Product ID # into the system
- Acme Pos Storage retrieves information about the product, delivery and availability
- Customer fills in Product ID# in slip and hands over to Sales Assistant
- Sales Assistant to check availability basis the number.
- If available, process payments with the customer
- Sales assistant to provide price details to customer
- Customer to pay by cash or credit card
- Transaction is saved in Transaction file.
- Customer is provided with receipt
- Order details are notified to staff in stock room
- Staff to search products in stock room
- Get it to the counter and inform customer on order ready
- Customer to collect the order at the counter
- Staff to update POS System on stock
- Basis product availability, periodically, place order
- Order placed to supplier basis information available in the supplier database
- Supplier to fill the stock quantity required basis order.
- Notify the delivery date to the POS System.