Introduction to UML For OOM

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Introduction to UML For OOM

• Outline the purpose of UML
• List key UML diagrams
• State their role in development
• Describe the components of a class diagram
• Inheritance (generalisation/specialisation)
• Aggregation (part/whole)
• Association (general links between classes)
• Tutorial http//dn.codegear.com/article/31863
• Various resources http//www.uml.org/

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Summary

• Introduction to OO methodologies and UML
• Outline of UML
• Use Case Diagrams
• Class Diagrams
• State Diagrams
• Sequence Diagrams
• Collaboration Diagrams
• Variety of Implementation Diagrams
• Class Models in UML
• Class diagrams

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Object-Oriented Modelling

• What is a Model?
• An abstract representation of system
• Why Model?
• Help thought communication
• Claims for OO Modelling
• objects closer to reality than functions
• Better representation
• E.g size of model change will relate to
  requirements change
• closer links between analysis and implementation
• If using OOP, should use OOM

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Methodologies for OO Modelling

• Many similar methods developed in 1980s
• (OOSE, OMT, Fusion, Booch (OOD))
• developed from OO programming languages
• based on structured methods
• SSADM, Yourdon, Structured Analysis
• Unified Modelling Language (1990s)
• collaboration by three key developers of OO
  methods
• Grady Booch, Ivar Jacobson, and Jim Rumbaugh.
• Unify best practice
• Set a standard for OO modelling methods.
• UML is standardised
• The Object Management Group (OMG)

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An Overview of UML

• A collection of compatible modelling techniques
• Not a modelling methodology
• allows use of appropriate approach for a project
• but offers no guidance

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UML Modelling Techniques

• Use Case Modelling
• Use case diagrams
• Use case descriptions
• Static Structure Diagrams
• Class diagrams
• Object diagrams
• Interaction Diagrams
• Sequence diagrams
• Collaboration diagrams

• State Diagrams
• State diagrams
• Activity diagrams
• Implementation Diagrams
• Package diagrams
• Component diagrams
• Deployment diagrams

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Diagram Overviews

• Use Case Diagrams
• interaction between system and external entities
  (actors)
• Use specification and testing
• Class Diagram
• classes and relationships between them.
• Single class model may use several diagrams for
  legibility.
• Use specification design
• Object Diagram
• diagram for relationships between specific
  objects.
• Use specification and design

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Interaction Diagrams

• Sequence Diagram
• How objects interact over time to handle a
  situation
• Timing of messages (methods called) between
  objects
• Use
• specification and design
• Collaboration Diagram
• An object diagram showing links between objects
  and using numbered arrows to indicate a sequence
  of events.
• Use
• specification and design

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State Activity Diagrams

• State Diagram
• How events change an object's state and its
  behaviour
• Use specification and design
• Activity Diagram
• Represents tasks performed by actors and
  interactions
• The closest thing to a flowchart in modern
  software development
• Use specification and design

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Implementation Diagrams

• Package Diagram
• Logical grouping of classes and packages
• Use detailed design
• Component Diagram
• How code is divided into physical modules.
• Use implementation
• Deployment diagrams
• The physical architecture of the application.
• Nodes usually represent hardware platforms.
• Use implementation

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UML Class Diagrams

• A class has
• name
• attribute components
• operation components
• Class diagram shows classes inter-relationships
• A diagram represents part of the class model
• A class in the model may appear on none, one or
  several diagrams

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Class Diagram Examples

• A simple class
• A class with attributes and operations

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Example parameterized class

• The List class definition leaves class T
  unspecified - possibly any class
• A template
• ltltbindgtgt is a stereotype
• Stereotypes give added information about UML
  components.
• The T class is replaced (bound to) by the Book
  class
• A BookList object is a list of Books

ltltbindgtgt(Book)
Listltintgt
An unnamed list of integers
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Class Members

• Attributes
• descriptive name
• type or class
• may have
• an initial value
• visibility
• Visibility Categories
• public - accessed by any client of the class
• protected accessed by descendants
• Also called derived classes / specialisations
• private - only by members of the same class

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Operations

• Every operation must have descriptive name
• An operation may have
• A return type
• Arguments
• Each argument must have a name and a type
• May have a default value
• Visibility

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Relationships

• 3 main types of relationship
• generalisation/specialisation (inheritance "is
  a")
• aggregation (whole-part has a and contains)
• association (any other relationship)

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Association

• Shows logical links between classes
• Multiplicity (cardinality) - number of objects
  involved
• exact number 1
• a range 2..5
• unspecified (many)
• Role and navigability how to read the
  association
• A copy is a copy of a book
• Navigability can be uni-directional or
  bi-directional
• Given an object at one end of the link, can we
  find the other end?
• Uni-directional links can be implemented by a
  pointer

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Qualified association

• A qualifier is a list of attributes whose values
  serve to partition the set of instances at the
  other end of the association.
• There will be 9 squares
• Each defined by a row, column value pair in the
  board

Qualifier attributes row column
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Derived association
takes
Student
Module
/teaches
delivers
Lecturer

• The 'teaches' relationship can be inferred from
  the others so need not be directly implemented
• A derived association is shown by the slash.
• The black triangles can be used on any
  association name to show how to read the
  association

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Xor-constraint

• A copy will be either a book or a journal

0..
Copy
Book
xor
0..1
Journal
The equivalent of a C Union
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Association classes

• Allows attributes and operations relating to the
  association to be specified explicitly

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Generalisation (Inheritance)

• One class is a specialized version of another
• Check for correctness check substitutability.
• Can use a specialised object in place of the
  ancestor
• NOT the other way around.
• The classes should be logically related
• Ask is child a sort of parent

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Aggregation

• Represent 'whole-part' relationships
• Aggregation one object can be included in
  another
• Composition one object is part of the structure
  of another
• Can the 'whole' be destroyed while the 'parts'
  remain ?
• yes aggregation
• no composition

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Summary

• UML is a standardised set of notations
• Can be used in different methodologies
• UML diagrams cover much of the lifecycle
• Class diagram shows part of a class model
• Class model displays static relationships
• Inheritance
• Aggregation
• Aggregation container
• Composition component parts
• Association