Domain Model Exercise: the Movie Shop

The following are the requirements for a web-based system to computerize the management of the sale and rental of movies for a movie shop.

• The system must be able to handle both physical and digital movies.
• It must be able to record which movies are sold and rented and by whom.
• For sold movies, the quantity sold should be recorded; for physical movie rental, which copy is rented and when it is due back should be recorded.
• The system should keep track of overdue rentals of physical movies and send email notices to customers who have movies overdue.
• There will be a customer membership option for an annual fee, which will entitle a member to discounts (10%) on the sale and rental of movies.
• Members should be able to make reservations for physical movie rentals either in person at the shop, by telephone or via the Web.
• A member can reserve at most five physical movies at any one time, but there is no limit on how many physical movies a member or nonmember can rent at any one time.
• As an added feature, the shop would like to allow customers (either members or nonmembers) to input, via the Web, mini-reviews (up to 100 words) and a rating (from 1, lowest, to 10, highest) of movies they have purchased or rented.

(c o n t'd )

• These reviews should be anonymous if the customer so wishes (i.e., customers can specify whether they want their name to be made known when other customers browse the reviews).
• A sales clerk should be able to enter and update the following information about all customers (members or nonmembers): name, address, phone number, age, sex, and email address.
• Members are assigned a membership number by the shop when they become members and a password, which allows them to change their personal information and to buy and rent digital movies via the Web.
• The shop manager should be able to generate various reports on the sale and rental of movies.
• A sales clerk should be able to sell and rent physical movies and process the return of rented physical movies.
• When selling or renting physical movies, a sales clerk must be able to look up customer information and determine whether the customer is a member.
• A sales clerk must be able to enter basic information about a movie (i.e., movie id, title, leading actor(s), director, producer, genre, synopsis, release year, running time, selling price, and rental price).

(c o n t'd)

From the movie sales and rental shop requirements statement:

a) identify all the classes, attributes, association classes,

associations, aggregations/compositions, generalizations and multiplicity constraints that are relevant to include in the domain model for the new system. (Only those that are explicitly given in or implied by the requirements statement should be included.)

b) Construct a class diagram showing how the classes

identified in (a) are related by associations, aggregations/ compositions and generalizations. Show the most likely multiplicities for all associations, making reasonable assumptions where necessary. If a multiplicity cannot be inferred from the requirements statement or common real-world domain knowledge, then indicate this with a “?” . Do not show the attributes of the classes in the class diagram.

We first analyze the requirements statement to determine the requirements for the domain model and then present the domain model.

• The system must be able to handle both physical and digital movies. classes: Movie attributes: Movie: isPhysical, isDigital
• It must be able to record which movies are sold and rented and by whom. classes & associations: Customer Purchases Movie Customer Rents Movie
• For sold movies, the quantity sold should be recorded; for physical movie rental, which copy is rented and when it is due back should be recorded. classes & associations: Movie Has RentalCopy Customer RentsPhysical RentalCopy attributes: Purchases: quantity RentalCopy: copyNumber, returnDate

• The system should keep track of overdue rentals of physical movies and send email notices to customers who have movies overdue. attributes: Customer: email
• There will be a customer membership option for an annual fee, which will entitle a member to discounts (10%) on the sale and rental of movies. generalization: Member is a kind of Customer → Customer Generalizes Member
• Members should be able to make reservations for physical movie rentals either in person at the shop, by telephone or via the Web. classes & associations: Member Reserves RentalCopy
• A member can reserve at most five physical movies at any one time, but there is no limit on how many physical movies a member or nonmember can rent at any one time. constraint: max-card(Member, Reserves) = 5 max-card(Customer, RentsPhysical) = *

• As an added feature, the shop would like to allow customers (either members or nonmembers) to input, via the Web, mini-reviews (up to 100 words) and a rating (from 1, lowest, to 10, highest) of movies they have purchased or rented. classes & associations: Customer Provides Review IsFor Movie → Customer Provides Review Review IsFor Movie attributes: Review: reviewText, rating
• These reviews should be anonymous if the customer so wishes (i.e., customers can specify whether they want their name to be made known when other customers browse the reviews). attributes: Review: anonymous
• A sales clerk should be able to enter and update the following information about all customers (members or nonmembers): name, address, phone number, age, sex, and email address. attributes: Customer: name, address, phoneNumber, age, sex, email

• Members are assigned a membership number by the shop when they become members and a password, which allows them to change their personal information and to buy and rent digital movies via the Web. attributes: Member: memberNumber, password
• The shop manager should be able to generate various reports on the sale and rental of movies. functional requirement: no new domain model requirements
• A sales clerk should be able to sell and rent physical movies and process the return of rented physical movies. functional requirement: no new domain model requirements
• When selling or renting physical movies, a sales clerk must be able to look up customer information and determine whether the customer is a member. functional requirement: no new domain model requirements

• A sales clerk must be able to enter basic information about a movie (i.e., movie id, title, leading actor(s), director, producer, genre, synopsis, release year, running time, selling price, and rental price). attributes: Movie: movieId, title, leadingActor[0..*], director, producer, genre, synopsis, releaseYear, runningTime, sellingPrice, rentalPrice

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Using “ids” to relate c

lasses

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Representing the client/organization (e.g., Shop) Incorrect use/overuse of generalization

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(e.g., Person, Nonmember, PhysicalMovie, DigitalMovie) Incorrect use/overuse of aggregation/composition

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(e.g., Movie<> —— RentalCopy, Movie<> —— Review,

Customer<> —— Member)

Incorrect use of association class

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Incorrect constraints (e.g., XOR)

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Representing operati

ons

(e.g., generates, browses, enters, looks up, etc.) Storing reports

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Representing implementation aspects

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(e.g., System, Web, telephone, reports)

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Over specifying the model (e.g., sales clerk, manager)

Key question: What information about things/

procedures needs to be persistent (i.e., in files or a database)?