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chaPter 10 • object-oriented systems analysis and design Using Uml 257

As the group decides which class is responsible for a particular function, the analyst who
owns the class for the session picks up that card and declares, “I need to fulfill my responsibil-
ity.” When a card is held in the air, it is considered an object and can do things. The group then
proceeds to refine the responsibility into smaller and smaller tasks, if possible. These tasks can
be fulfilled by the object if it is appropriate, or the group can decide that it can be fulfilled by
interacting with other things. If there are no other appropriate classes in existence, the group may
need to create one.
The four CRC cards depicted in Figure 10.3 show four classes for course offerings. Notice
that in a class called Course, the systems analyst is referred to four collaborators: the depart-
ment, the textbook, the course assignment, and the course exam. These collaborators are then
described as classes of their own on the other CRC cards.
The responsibilities listed will eventually evolve into what are called methods in UML.
The Object Think statements seem elementary, but they are conversational so as to encourage a
group of analysts during a CRC session to describe as many of these statements as possible. As

Figure 10.3
Four CRC cards for course
Class Name: Department
Superclasses: offerings show how analysts
Subclasses: fill in the details for classes,
Responsibilities Collaborators Object Think Property responsibilities, and collaborators,
Add a new department Course I know my name Department Name as well as for Object Think
Provide department information I know my department chair Chair Name statements and property names.

Class Name: Course
Superclasses:
Subclasses:
Responsibilities
Collaborators
Add a new course Object Think Property
Department
Change course information I know my course number Course Number
Textbook
Display course information I know my description Course Description
Assignment
I know my number of credits
Exam Credits
Class Name: Textbook
Superclasses:
Subclasses: Property
Responsibilities Collaborators Object Think ISBN
Add a new textbook Course I know my ISBN Author
Change textbook information I know my author Title
Find textbook information I know my title Edition
Remove obsolete textbooks I know my edition
I know my publisher Publisher
I know if I am required Required

Class Name: Assignment
Superclasses:
Subclasses:
Responsibilities
Collaborators
Add a new assignment Object Think Property
Course
Change an assignment I know my assignment number
Task Number
I know my description
View an assignment
Task Description
I know how many points I am worth
Points
I know when I am due
Due Date