Object Oriented Design Using UML

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Object Oriented Design Using UML

• IntroductionUML and Modeling
• Objects and Classes
• Finding Classes
• Relationships
• Operation and Atributes
• Class Diagram and Template Codes

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IntroductionWhat Is the UML?

• The Unified Modeling Language (UML) is a language
  for
• Specifying
• Visualizing
• Constructing
• Documenting
• the artifacts of a software-intensive system

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Introduction Why Modeling?
A Language Is Not Enough
Team-Based Development
Modeling Language
Process
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Object and Class

• Class describe s a group of objects with similar
  properties(attributes), common behavior(operations
  ), common relationships to other objects and
  common semantics.
• Semantics depends on purpose of application
  i.e.building, machines may belong to different
  classes or same classes if regarded as financial
  assets.
• Abstraction is achieved by grouping objects into
  classes

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Class and Objects

• Difference between class and objects
• Class has 3 compartments
• Name
• Attribute
• Operation

Class with attributes
Objects with values
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Attributes

• Attributes is a data value held by the objects in
  the class
• Specify name, type, and optional default value
• attributeName Type Default
• Type should be elementary data type in
  implementation language
• Built-in data type, user-defined data type

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Operations

• Is a function
• All objects in a class share the same operations.
• Each operation name may be followed by optional
  details (opreations signature) i.e. argument list
  and result type
• Operation(arg namearg type default)return

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Object and Class Naming Conventions

• Naming Class starts with a capital letter and
  also for the second word
• i.e. DegreeStudent
• Naming attributes and operations starts with a
  small letter and second word starts with capital
  letter
• i.e. getGrade()
• No hyphenation between words
• Post-Graduate-Student

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Objects and Class

• Class Notation in UML

Example student class
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Finding Classes

• i) Method to find objects and their classes
• Begin with the nouns in the requirements
  specification.
• ii) Method to find operations
• Begin with the verbs in the requirements
  specification.
•  Example Computerized Telephone Book For A
  University
• The telephone book should contain entries
  for each person in the university
  community--student, professor, and staff member.
  Users of the directory can look up entries. In
  addition, the administrator of the telephone book
  can, after supplying a password, insert new
  entries, delete existing entries, modify existing
  entries, print the telephone book, and print a
  listing of all students or of all faculty.

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Finding Classes

• 1. Identify the candidate classes. List the
  nouns and noun phrases from the specification
•   computerized telephone book, university,
  telephone book, entry, person, university
  community, student, professor, staff member,
  employee, user, administrator, password.
• 2. Identify the candidate operations. List the
  verbs from the specification.
•   lookup entry, supply password, insert new
  entry, delete existing entry, modify existing
  entry, print telephone book, print all students,
  print all employees, set telephone number field,
  get telephone number field, compare entries.

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• 3. Eliminate unnecessary and synonym classes and
  operations.
•   For example, computerized telephone book,
  telephone book, and directory can be combined
  into a single PhoneBook class.
• 4. Associate the operations with the
  appropriate classes.
•   For example, associate lookup, insert,
  delete, and modify entry operations with the
  PhoneBook class, associate compare,
  setPhoneNumber and getPhoneNumber with the Person
  class, etc.

During design we should not be concerned with the
minute details of the implementation. However, it
is appropriate to consider whether there is a
"reasonable" implementation.
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Relationships Object Interactions

• Association
• Multiplicity
• Role
• Qualified association
• Association as a class
• Aggregation
• Generalization/Inheritance

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Relationships/LinksAssociation
Association between classes
Instance association
- When there is association between classes,
instances/objects of the class has association. -
Although associations are bidirectional, they do
not have to be implemented in both directions.
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Association Multiplicity

• Specifies how many instances of one class may
  relate to a single instance of an associated
  class.
• i.e.

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Association Role

• A role name is a name that uniquely identifies
  one end of an association.
• Written next to the class that plays the role.
• i.e.

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AssociationQualified Association

• Can be used as a key to access data.
• One to many and many to many associations may be
  qualified.
• i.e.
• One lecturer teach a lot of students (1..).
  Metricno is used to identify the student.

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Relationships/Links Aggregation

• Aggregation is the part-whole or a-part-of
  relationship
• objects representing the components are
  associated with an object representing whole
  components.
• i.e. part- of

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Relationships/Links Aggregation

• part-whole

whole
part
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Relationships/Links Generalization

• is-a or a kind of relationship
• Generalization is the relationship between a
  class and one or more refined versions of it.
• Example

General
Refined
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Relationships/Links Generalization

• The general class is called superclass.
• Each refined version is called a subclass.
• Attributes and operations common to a group of
  subclasses are attacthed to superclass.
• Each subclass inherits the features of it
  superclass.

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Aggregation vs Generalization

• Relates instances
• Composed of object instances that are all part of
  composite object
• part-whole or
• a-part-of relationship

• Relates classes
• Composed of classes that describe an object
• is-a or a kind of relationship

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Class Diagram Student Registration

• Show static modeling elements i.e classes and
  their relationships.

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Template Code Student Registration
class Student String name float CPA
float GPA String generateSlip(String
result) CPA 0.0 GPA 0.0 return
result class GraduateStudent extends
Student String scholarships float
scholarshipsAmount void getProject()
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Template Code Student Registration

• class PostGraduateStudent extends Student
• boolean workingExperience
• void getThesis()
• class DiplomaStudent extends Student
• boolean practicalTraining
• void getTraining()

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Template Code Student Registration

• class Subject
• String code
• float credit
• CoreSubject CSubject
• ElectiveSubject ESubject
• int register()
• return
• class CoreSubject
• float passingGrade
• float getGrades
• return

• class ElectiveSubject
• boolean seminar
• class Lecturer
• public static void main(String args)