Develop an EER model for the following situation. You need to make your own (rea
ID: 3884910 • Letter: D
Question
Develop an EER model for the following situation. You need to make your own (reasonable) assumptions regarding the relationship cardinality if it is not explicitly indicated. Show your assumptions in your solution. You need to indicate which attribute you choose for the identifier of each entity type. You may create an identifier attribute if needed.
A technology company provides offerings to its customers. Offerings are of two separate types: products and services. Offerings are identified by an offering ID and an attribute of description. In addition, products are described by product name, standard price, and date of first release; services are described by name of the company’s unit responsible for the service, conditions of service, and the service type. There are repair, maintenance, and other types of services. A repair service has a cost and is the repair of some product offered by the company; a maintenance service has an hourly rate. The company wants to keep track of repair services on products with repair date and a short description of the issue. Some products may never require repair, but there are many potential repair services for a product. A customer may purchase an offering, and the company needs to keep track of when the offering was purchased and the contact person for that offering with the customer. Unfortunately, not all offerings are purchased. Customers are identified by customer ID and have descriptive data of name, address, and phone number. When a service is performed, that service is billed to the customer. When a customer is billed for a service (some customers may never require a service), the company wants to keep track of the service date, the due day of the bill, and the amount due.
Explanation / Answer
An ERD is a graphical description of the data for a particular database = a graphical data model. It represents the data at a high level of abstraction
“An entity is a ‘thing’ or ‘concept’ or ‘object’. Well, most of the time”.
An entity [type] is not a single ‘thing’ but rather a representation of like or similar things that share characteristics (properties). For example, King Lear and Hamlet are both plays and have properties such as name, author, cast of actors and lines of verse. The entity [type] describing these might be PLAY, with King Lear and Hamlet as examples of instances or occurrences of PLAY [
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