Management of a variety store has decided to implement a computerized Inventory System to give the store capability to track and record every transaction from the purchase of goods from suppliers, purchases made by customers, available stock, and when to replenish stocks. Management will receive reports daily and monthly summary reports on purchase orders, invoices, customer purchases and stock inventory. Stock levels will be updated immediately that purchases and sales are made to give a clear indication of the amount of stock to be ordered within a timely manner.
A Purchase Order is prepared by a Clerk and sent to a Supplier via e-Mail. The Purchase Order gives the quantity required, a description of the various items, the cost of each batch and the total cost which includes the Value Added Tax (VAT), and the date on which the goods should be delivered. All Purchase Orders are entered into a Purchase Orders database. On receipt of the Purchase Order, the supplier acknowledges receipt via e-Mail as well as confirms that the goods will be delivered on the date requested. If the price of any item is different to that stated on the Purchase Order, the Supplier quotes the correct price on an Invoice which is e-mailed with the acknowledgement. The Clerk uses the supplier invoice to generate several individual invoices in an Invoices database and updates the original purchase order in the Purchase Orders database with updated prices where necessary. The Clerk creates a separate invoice for each individual item on a Purchase Order. One invoice can be created for the same item on more than one purchase order.

Each item in the Stock Inventory database has a unique bar code identifier. When delivering the goods the Supplier delivers a Delivery Notice listing all individual items. On receipt of the ordered goods, one item from each batch purchased is scanned to the system and the Inventory database updated with the quantity purchased. At the end of stocktaking, a notification is sent to the Accounts Department and to the Supplier on a Delivery Form indicating the quantity of each item of goods received and the items considered ‘unfit for sale'. The Delivery Form indicates whether or not all goods received were in good order for sale to customers. The Supplier e-mails an updated Invoice to the Purchasing Department and the Clerk updates the individual invoices where necessary. The Accounts Department will make payment to the supplier based on the final invoice received.

Each item purchased by a customer is captured in a separate database. The cash registers are linked to the Inventory System so that when the cashier at the Store scans each item purchased by a customer, the stock level of the item is reduced by the amount purchased. This allows the Purchasing Department to know when to order a particular item and in what quantity. The customer is provided with a receipt when payment is made and all receipts are written to a database.

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1) Assume you are required to design an Entity-Relationship diagram for a database in which all information pertaining to the inventory system is to be stored. Given the information in the case, state all the E-R entities and use them to sketch an E-R Diagram showing both maximum and minimum cardinalities for each relationship in the diagram. State ALL assumptions made to arrive at the cardinalities.

2) For all E-R entities, provide the primary key attribute and three (3) or more other attributes (make up these where the information from the case proves insufficient).

3) For all relationships in your E-R diagram above, show the database tables for a relational database design. Provide at least one attribute along with the primary key attribute for any new table derived.