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CHAPTER 9 Software Design 141<br />
Answers to Review Questions<br />
1. Given the following design, indicate for the following ideas of coupling, cohesion, and<br />
abstraction whether it is desirable to have a high or low value and how this design<br />
exemplifies the term.<br />
Class college<br />
student* stulist[MAX]<br />
course* courselist[MAX]<br />
public:<br />
addStudent(char* studentname)<br />
addStudentToCourse(char* studentname, char*<br />
coursename)<br />
void displayStudent(char* studentname)<br />
void displayStudentsInCourse(char* coursename)<br />
Class course<br />
student* classroll[MAX]<br />
public:<br />
void displayStudents()<br />
Class student<br />
char* name<br />
public:<br />
void displayname()<br />
Coupling—Low coupling is desirable, and this design has low coupling, since the<br />
college class has no knowledge of the internals of the other classes and the other<br />
classes do not need to know about college.<br />
Cohesion—High cohesion is desirable, and this has high cohesion, since each class just<br />
deals with its own attributes.<br />
Abstraction—The design shows good abstraction. For example, the display method in<br />
college does not include any details about lower-level display methods.<br />
2. Why does Gunter restrict the terms/events that can be used in a specification? What is<br />
the difference between a user’s requirements and a specification?<br />
Gunter says that a user’s requirements must be specified in terms/events that are<br />
known to the user and may include terms/events hidden to the machine, while a<br />
specification is designed to be the basis of the implementation and must be specified<br />
only in terms that are visible both to the machine and the world.<br />
3. The proposed system is a face recognition based on image processing. The system will<br />
have a camera and is intended to prevent nonemployees from entering the company’s<br />
secret facilities by controlling the lock on the door. When a person tries to turn the<br />
door handle, the system takes an image and compares it with a set of images of current<br />
employees.<br />
Classify each of the following events as to whether the events are in the environment<br />
or in the system and whether the events are hidden or visible:
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