02/03/2010
ITEX
ITEX is a store in Auckland that assembles and sells a range of IBM compatible computers to resellers and individual customers on demand.
ITEX purchase parts from a variety of suppliers, both in NZ and overseas and use the parts to assemble a range computers based on the orders. A part may be supplied by many suppliers and each supplier may supply many parts. Once supplied, a supplier's invoice will have at least one line item and obviously the line item will belong to only one invoice. The line item will represent one part because each part may be involved in many invoice line items.
ITEX uses the parts to build computers based on the customer orders. So each computer is made up of one or more parts and a part may be used in many such computers.
When the computer is ready an invoice is generated. Each sales invoice has at least one invoice line item. Obviously the line-item will belong to only one invoice. A line item will be for one computer and so each such computer may be involved in many invoice line items. A sales invoice must be for one customer.
These invoices are based on the customer orders. An order from a customer must be for at least one computer. Such a computer may be involved in many customer orders. An order may generate one or more invoices.
- Identify the main entity types of ITEX.
- Identify the main relationship types between the entity types described in (a) and represent each relationship as an ER diagram.
- Determine the multiplicity constraints for each relationship described in (b). Represent the multiplicity for each relationship in the ER diagrams created in (b).
- Identify attributes and associate them with entity or relationship types. Represent each attribute in the ER diagrams created in (c).
- Determine candidate and primary key attributes for each entity.
- Using your answers (a) to (e) attempt to represent the data requirements of ITEX computer store as a single ER diagram. State any assumptions necessary to support your design.
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