Data Modeling Patterns The textbooks talks about the relationships between user
ID: 3649165 • Letter: D
Question
Data Modeling PatternsThe textbooks talks about the relationships between user forms and reports and their underlying database structure. There are well-known structures used in forms and reports that translate into well-known patterns that appear regularly in an ERD (entity relationship diagram) database model.
Describe one of these data modeling patterns, along with an example of when it would be used. Do not use the examples given in the textbook.
Have you seen any of these well-known patterns in forms or reports you have encountered at work or on the Internet? Give an example and explain what it lets you infer about the underlying structure of the database behind it.
Explanation / Answer
When designing a business information system, it's important to start with a good database design. A good design makes it possible-even easy-to answer the questions the business needs answered, and to generate the reports the business needs. A poor design makes these tasks difficult or impossible. Often, poor database designs-along with the data already entered and the programs, forms, and reports already written-are discarded in favor of a better design, resulting in lost time and money. The goal of entity-relationship design is two-fold: to understand our data, and to design a database that properly represents this data. In the beginning, however, don't think of tables and databases. Instead, we concentrate on entities and attributes, and the relationships between them. To use entity-relationship design, you need a good understanding of the business situation involved. You need to be able to identify the "things" that the business needs to track. You must also be able to identify the relationships between these things. In other words, you need to know about the business situation. Generally, you'll obtain this information through your own knowledge of the business, through interviews with the users and managers, by examining the reports and forms the business already uses, and through other techniques. It's likely that during the model-building process you'll learn additional things about the business and clarify the meanings of the data the business uses. As an example of entity-relationship design, consider the case of the Pine Valley Video Tape Club, which is seeking to implement its records on a computer. The club has members (customers) and a collection of tapes available for rental. The purpose of the system is to track membership, tape inventory, and tape rental activity. For each member, the club wants to keep track of these data items: A unique identification or membership number The member's name The member's address The date that the member joined the club The tapes the member has rented, along with the date that each tape is due In real life, the club would need members' city, state, zip code, telephone number, credit card number, and perhaps other information. For each tape, the club wants to keep track of these items: The tape's identification number, which is printed on the bar code applied to each tape. It's possible that the club may have more than one copy of any movie title. The tape's title The tape's rating (G, PG-13, R, and so forth) The tape's rental charge (popular movies and recent releases may be more expensive to rent) The date the club purchased the tape The purchase price the club paid for the tape The supplier (who the club bought the tape from) The supplier's address When a member rents a tape, the club needs to keep track of these items: The date of the rental The due date for return of the tape The date the tape was returned The rental fee Members must return rented tapes in four days, and each member has a limit of five tapes rented out at any time. Here are some sample questions that the club wants to be able to answer: List the names of the member who joined the club in a particular month. Members often ask for G-rated movies for family viewing. List tapes with a G (or any other) rating. Produce a list of G-rated movies again, but this time include only those movies that the customer has not yet rented. How many copies do we have of each of our tapes? List the tapes that are currently rented. List the tapes that are currently rented for each member. List the overdue tapes. Are there any members who have yet to rent a tape? Of course, other questions will arise as the business begins to use the database.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.