1. Software Engineering System Modeling Chapter 5 (Part 2) Dr.Doaa Sami
Modified from Sommerville’s originals

2. 2
C. Structural Models

3. What is a Domain Model?
Use cases looked at the system’s environment (actors) and the system’s external behavior.
Use cases consider the system as a black box and help us understand how the system as a whole interacts with the outside word.
Now we turn to consider the inside of the system. We do this by building the domain model, which shows what the black box (the system) encloses.
uses cases elaborate the system’s behavioral characteristics (sequence of stimulus-response steps),
domain model gives details of the systems structural characteristics (system parts and their arrangement)
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4. What is a Domain Model?
uses cases elaborate the system’s behavioral characteristics (sequence of stimulus-response steps),
domain model gives details of the systems structural characteristics (system parts and their arrangement)
The next step is to model the inside of the system. We do this by building the domain model, which shows what the black box (the system) encloses.
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5. 3
1. C l a s s D i a g r a m

6. Structural Models 4
 Structural models of software display the organization of a system in terms of the components that make up that system and their relationships.
 You create structural models of a system when you are discussing and designing the system architecture.
 Class diagrams used for modeling the static structure of the object classes in a software system.

7. Class Diagram attributes, operations, relationships and behaviors.5
 A class represent a concept.
 It is a description of a set of objects having similar
attributes, operations, relationships and behaviors.
 A class encapsulates state (attributes) and behavior
(operations).
 The Class Name is the only mandatory information.
Class Name
Attribute
Operation()

8. From Use Cases to: Objects, Attributes, Operations (methods) -“evolutionary ”
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9. Building the Domain Model
A useful strategy for building a domain model is to start with:
the “boundary” concepts that interact directly with the actors
and then identify the internal concepts
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10. Domain Model Relationships
Conceptual Class Diagram
Classes, attributes, associations
Domain objects
Use Case Model
Functional Requirements
Domain Model
Define terms
Glossary
Interaction Diagrams
Dynamic Behavior
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11. Steps to create a Domain Model
Identify Candidate Conceptual classes
Draw them in a Domain Model
Add associations necessary to record the relationships that must be retained
Add attributes necessary for information to be preserved
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12. Finding Classes 6
Categories to focus when finding represent-able objects:
 Tangibles (e.g. classroom, playground).
 Conceptual (e.g. course, module).
 External Organizations (e.g. publisher, supplier).
 Roles Played (student, teacher).
 Other System (admission system, grade reporting system).

13. 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

14.  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

15. Find conceptual classes
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16. Use a category list Finding concepts using the concept category list :
Physical objects: register, airplane, blood pressure monitor
Places: airport, hospital
Catalogs: Product Catalog
Transactions: Sale, Payment, reservation
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17. Identifying objects
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18. Identifying Operations ‘methods’
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19. Objects
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20. Example: Identify conceptual classes from noun phrases
Consider the following problem description, analyzed for Subjects, Verbs, Objects:
The ATM verifies whether the customer's card number and PIN are correct.
SC V R O O A O A
If it is, then the customer can check the account balance, deposit cash, and withdraw cash.
S R V O A V O A V O A
Checking the balance simply displays the account balance.
S M O A V O A
Depositing asks the customer to enter the amount, then updates the account balance.
M S V O R V OA V OA
Withdraw cash asks the customer for the amount to withdraw; if the account has enough cash,
S M A O V O R OA V S C V O A
the account balance is updated. The ATM prints the customer’s account balance on a receipt.
O A V C S V O A O
Analyze each subject and object as follows:
Does it represent a person performing an action? Then it’s an actor, ‘R’.
Is it also a verb (such as ‘deposit’)? Then it may be a method, ‘M’.
Is it a simple value, such as ‘color’ (string) or ‘money’ (number)? Then it is probably an attribute, ‘A’.
Which NPs are unmarked? Make it ‘C’ for class. Verbs can also be classes, for example:
Deposit is a class if it retains state information
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21. Mapping parts of speech to object model components [Abbott, 1983]
Part of Speech
Model Component
Examples
Proper noun
Instance
Ali
Common noun
Class
Student, Customer,..
Doing verb
Operation
Buy, check,..
Being verb
Inheritance
Is a kind of, is one of either
Having verb
Aggregation (Composition)
Has, consists of, includes
Modal verb
Constraints
Must be
Adjective attributes
Attributes
3 years old
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22. Example: a typical description
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23. Mapping parts of speech to object model components
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24. Example: Initial POS domain model
SalesLineItem
Register
Item
Store
Sale
Payment
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25. 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.

26. Associations
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27. 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

28. 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

29. 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();
}; } ;

30. Multiplicity Representation13

31. Multiple association between two classes
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32. Example: Initial POS domain model
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33. Example: Initial Domain model of the Monopoly Game
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34. Example: Domain model of the Monopoly Game
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35. 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

36. 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.

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

38. 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.

39. 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.

40. Generalization 19

41. 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.

42. Example: Information System for School21

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48. Class or Attributes
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49. Class or Attributes
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50. Description Class
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