SEG4110 Advanced Software Design and Reengineering

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SEG4110 Advanced Software Design and
Reengineering

• TOPIC A
• Review of UML

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5.1 What is UML?

• The Unified Modelling Language is a standard
  graphical language for modelling object oriented
  software
• At the end of the 1980s and the beginning of
  1990s, the first object-oriented development
  processes appeared
• The proliferation of methods and notations tended
  to cause considerable confusion
• Two methodologists Rumbaugh and Booch merged
  their approaches in 1994.
• They worked together at the Rational Software
  Corporation
• In 1995, another methodologist, Jacobson, joined
  the team
• His work focused on use cases
• In 1997 the Object Management Group (OMG) started
  the process of UML standardization

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Classes

• A class is simply represented as a box with the
  name of the class inside
• The diagram may also show the attributes and
  operations
• The complete signature of an operation is
• operationName(parameterName parameterType )
  returnType

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Naming classes

• Use capital letters
• E.g. BankAccount not bankAccount
• Use singular nouns
• Use the right level of generality
• E.g. Municipality, not City
• Make sure the name has only one meaning
• E.g. bus has several meanings

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Labelling associations

• Each association can be labelled, to make
  explicit the nature of the association

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Analyzing and validating associations

• Many-to-one
• A company has many employees,
• An employee can only work for one company.
• This company will not store data about the
  moonlighting activities of employees!
• A company can have zero employees
• E.g. a shell company
• It is not possible to be an employee unless you
  work for a company

worksFor
1
Employee
Company

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Analyzing and validating associations

• Many-to-many
• A secretary can work for many managers
• A manager can have many secretaries
• Secretaries can work in pools
• Managers can have a group of secretaries
• Some managers might have zero secretaries.
• Is it possible for a secretary to have, perhaps
  temporarily, zero managers?

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Analyzing and validating associations

• One-to-one
• For each company, there is exactly one board of
  directors
• A board is the board of only one company
• A company must always have a board
• A board must always be of some company

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Analyzing and validating associations

• Avoid unnecessary one-to-one associations
• Avoid this do this

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Association classes

• Sometimes, an attribute that concerns two
  associated classes cannot be placed in either of
  the classes
• The following are equivalent

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Reflexive associations

• It is possible for an association to connect a
  class to itself

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Directionality in associations

• Associations are by default bi-directional
• It is possible to limit the direction of an
  association by adding an arrow at one end

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Object Diagrams

• A link is an instance of an association
• In the same way that we say an object is an
  instance of a class

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An Example Inheritance Hierarchy

• Inheritance
• The implicit possession by all subclasses of
  features defined in its superclasses

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The Isa Rule

• Always check generalizations to ensure they obey
  the isa rule
• A checking account is an account
• A village is a municipality
• Should Province be a subclass of Country?
• No, it violates the isa rule
• A province is a country is invalid!

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Inheritance, Polymorphism and Variables
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Avoiding unnecessarygeneralizations
Inappropriate hierarchy of classes, which should
be instances
Improved class diagram, with its
corresponding instance diagram
RecordingCategory
RecordingCategory
video
audio
subcategory
subcategory
subcategory
subcategory
subcategory
RecordingCategory
RecordingCategory
RecordingCategory
RecordingCategory
RecordingCategory
rock
blues
classical
jazz
music video
Recording
Recording
Let it be
9th Symphony
The Beatles
Beethoven
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Avoiding having instances change class

• An instance should never need to change class

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5.6 More Advanced Features Aggregation

• Aggregations are special associations that
  represent part-whole relationships.
• The whole side is often called the assembly or
  the aggregate
• This symbol is a shorthand notation association
  named isPartOf

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Composition

• A composition is a strong kind of aggregation
• if the aggregate is destroyed, then the parts are
  destroyed as well
• Two alternatives for addresses

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Interfaces

• An interface describes a portion of the visible
  behaviour of a set of objects.
• An interface is similar to a class, except it
  lacks instance variables and implemented methods

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Introduction to OCL
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Use Case Diagrams
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Example of generalization, extension and inclusion
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Example Description of a Use Case
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Sequence diagrams an example
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Sequence Diagrams an example with replicated
messages

• An iteration over objects is indicated by an
  asterisk preceding the message name

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Sequence Diagrams an example with object
deletion

• If an objects life ends, this is shown with an X
  at the end of the lifeline

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State Diagrams an Example of Transitions with
Time-outs and Conditions
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State Diagrams Example with Conditional
Transitions - CourseSection class
Planned
openRegistration
closeRegistration
requestToRegister (aStudent)
OpenNotEnoughStudents
Cancelled
cancel
/createRegistration
classSize gt minimum
cancel
closeRegistration
requestToRegister (aStudent)
Closed
OpenEnoughStudents
classSize gt maximum
/createRegistration
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State Diagram An Example with Substates
CourseSection Class Again
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State Diagram an Example with Actions Garage
Door Opener
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Nested Substates and Guard Conditions A Cars
Automatic Transmission

• A state diagram can be nested inside a state.
• The states of the inner diagram are called
  substates.

selectReverse
Reverse
Neutral
selectNeutral
selectDrive
selectFirst
selectSecond
selectNeutral
reachThirdSpeed
reachSecondSpeed
driveSelected
driveSelected
dropBelowThirdSpeed
dropBelowSecondSpeed
driveSelected
selectFirst
selectSecond
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Activity Diagrams An Example Course
Registration
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Package Diagrams
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Example of Multi-Layer Systems
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Component Diagrams
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An Example of a Distributed System
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Example of a Broker System
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Example of a Pipe-and-Filter System -Sound
Processing
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Example of the MVC Architecture for a User
Interface
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Example of the Service-Oriented Architecture
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Abstraction-Occurrence
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Abstraction-Occurrence

• Square variant

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General Hierarchy
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Player-Role
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Singleton
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Observer
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Delegation
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Façade
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Proxy
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Deployment Diagrams