Case Study
The Variety
Store
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.
c) Project Part C – E-R Diagram and Database Design
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.
