1. Software Engineering System Modeling Extra examples Dr.Doaa Sami
Modified from Sommerville’s originals

2. 2
C. Structural Models

3. 3
1. C l a s s D i a g r a m

4. attribute values +getlength(): double
Class Attributes 7
 Visibility name : type [count] = default_value
 underline static attributes Student
 Visibility name: string
 +  public totalStudent:int
#  protected getName(): string
 -  private getTotalStuden()t:int
 /  derived
 derived attribute: not stored, length: double
-width:double
attribute values getlength(): double
+getArea(): double
- salary: double
+ getSalary(): double
Rectangle
/area:double
but can be computed from
other
+getWidth():double

5.  Visibility -name: string
Class Operations 8
 Visibility name (parameters) : return_type
 underline static operations Student
 Visibility name: string
 +  public totalStudent:int
 # protected getName(): string
 -  private getTotalStuden()t:int
return_type is omitted if function is: Rectangle
 constructor length: double
 void width:double
+getlength(): double
+getWidth():double
+getArea():double
- salary: double
+ getSalary(): double
/area:double

6. Relationships 9  There are two kinds of Relationships
 Association (student enrolls in course).
 Generalization (parent-child relationship).
 Associations can be further classified as
 Aggregation.
 Composition.

7. Association  Associations denote relationships between classes.10
 Associations denote relationships between classes.
 Describe the nature of the relationship.
 Example:
 Student enrolls into course
 Course enrolled by a student.
Student Course
Enrolls

8. Multiplicity relates to ONE instance of another class.11
 Multiplicity is the number of instances one class
relates to ONE instance of another class.
 For each association, there are two multiplicity
decisions to make, one for each end of the
association.
 For each instance of Professor, many Sections may be taught.
 For each instance of Section, there may be either one or zero
Professor as the instructor.
Professor Section
-name:string has * -section#:int
+getName():string getSection#:int

9. Multiplicity (C++ Implementation)12
Professor Section
-name:string has * -section#:int
+getName():string getSection#:int
class Professor{ class Section{
// A list of Sections // Proffessor Section sec[4]; Professor prof; string name; int sectionNum;
Public: Public:
string getName(); int getSectionNum();
}; } ;

10. Multiplicity Representation13

11. Aggregation models a whole-part relationship between an14
Association is used when both of the involved classes are equaly important.
 Aggregation is a special form of association that
models a whole-part relationship between an
aggregate (the whole) and its parts.
 Aggregation shows how classes that are collections are composed of other classes.
 Aggregation is a part-of relationship.
Car Wheel

12. Composition 15  Composition is a strong form of aggregation.
 Aggregation is used to model a whole-part relationship between an aggregate (whole) and its parts.
 Composition is a strong form of aggregation.
 The whole is the only owner of its part.
 Multiplicity on the whole side must be one.
 The lifetime of the part is dependent upon the whole.
 When Circle is destroyed, Point is also destroyed.
 The composite must manage the creation and destruction of its parts.

13. Composition (C++ Implementation)16
Restaurant Menu
class Restaurant{ class Menu{ };
Menu m; };
....

14. Generalization Cows and Wolfs are Mammals. 17
Rather than learn the detailed characteristics of every entity that we experience, we place these entities in more general classes (animals, cars, houses, etc.) and learn characteristics of these classes.
 This allows us to infer that different members of these classes have some common characteristics e.g.
Cows and Wolfs are Mammals.

15. Generalization Cont. 18
 In object-oriented languages, generalization is implemented using class inheritance mechanisms.
 In a generalization, the attributes and operations associated with higher-level classes (super classes) are also associated with the lower-level classes (sub classes).
 Subclasses are inherit the attributes and operations from their Superclasses and then add more specific attributes and operations.

16. Generalization 19

17. Association Class association connection to have operations and20
 An association class is a construct that allows an
association connection to have operations and
attributes.
 It used when you need to include another class
because it includes valuable information about the
relationship.

18. Example: Information System for School21