WKES2304: Object Oriented Modeling

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WKES2304 Object Oriented Modeling

• Chapter 2 Introduction to Unified Modeling
  Language (UML)

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Chapter Outline

• UML History
• UML Overview
• Where can UML be used?
• 3 Recommended steps to understand UML
• Example Modeling the Hello World program

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UML History

• Object-oriented modeling languages appeared
  sometime between the 70s and 80s, as an
  experiment with alternative approaches to
  analysis and design
• the number of OO methods increased to more than
  50 by 1994
• problem arose in finding a modeling language that
  can satisfy users needs
• led to the so-called methodology war

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• 3 clearly prominent methods emerged from the
  so-called methodology war
• Booch methods expressive during the design and
  construction phase of projects
• Jacobsons Object Oriented Software Engineering
  (OOSE) - provides excellent support for use cases
  as a way to capture and analyse requirements and
  high-level designs
• Rambaughs Object Modeling Technique - useful for
  analysis and data-intensive information system
• The combination of these 3 methods led to the
  creation of the Unified Modeling Language, UML
• the UML definition strives to make the best
  trade-offs in each of these areas

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UML Overview

• UML is a standard language for writing software
  blueprints
• it is only a language
• it is NOT a process, just part of a software
  development method
• it is process independent

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• UML is a language for
• visualizing
• specifying
• constructing
• documenting
• the artifacts of a software-intensive system.

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The UML is a language

• A language provides vocabulary and the rules for
  combining words in that vocabulary for the
  purpose of communication
• A modeling language is a language whose
  vocabulary and rules focus on the conceptual and
  physical representation of a system
• thus, UML is a standard language for s/w
  blueprints
• helps in the understanding of a system
• may need more than one model
• UML tells you how to create and read well-formed
  models
• but does not tell you what models you should
  create and when you should create them
• that is the role of the s/w development process

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UML is a language for Visualizing

• Typical practice Thinking (idea) and then
  transform it into code
• still doing some modeling, informally and
  mentally
• sometimes scribble ideas on notepad or whiteboard
• problems with this approach
• errors in communicating these models, unless
  everyone involved speaks the same language
• using textual programming language to model a
  system does not make it easier to understand the
  system
• If the models used for building the programming
  code were never documented, it will be lost
  forever, or difficult for the programmer to
  recreate it

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• By writing models in the UML, these problems can
  be overcome -
• An explicit and formal model like the UML
  facilitates communication
• By writing down the model in a formal language,
  people who knows the modeling language can
  understand and read the models built
• Behind each symbol in the UML notation is a
  well-defined semantics/meaning
• Very useful especially for large project with
  many abstract ideas and processes
• Since UML is a graphical language, it transcends
  what can be represented in a programming language

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UML is a language for Specifying

• Here, specifying means building models that are
  precise, unambiguous and complete
• The UML addresses the specification of all the
  important analysis, design and implementation
  decisions that must be made in developing and
  deploying a software-intensive system

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UML is a language for Constructing

• The UML models can be directly connected to a
  variety of programming language
• It is possible to map from a model in the UML to
  a programming language such as Java, C etc
• This mapping permits forward engineering
• The generation of code from a UML model into a
  programming language

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UML is a language for Documenting

• The UML addresses the documentation of a systems
  architecture and its details
• The UML also provides a language for expressing
  requirements and for tests
• The UML also provides a language for modeling the
  activities of project planning and release
  management
• The combination of UML models and other kinds of
  work products that come out of a development
  effort generally forms a solid set of project
  documentation.

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Where can UML be used?

• It is primarily for software-intensive systems
• Enterprise information system
• Banking and financial system
• Telecommunication
• Transportation
• Defense/aerospace
• Retail
• Medical electronics
• Scientific
• Distributed web-based services

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3 Recommended steps to understand UML

• Requires learning 3 major elements-
• The UMLs basic building block
• The rules that dictate how those building blocks
  may be put together
• Some common mechanisms that apply throughout the
  UML

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1) The basic building blocks of the UML
Diagrams
Class diagram Object diagram Use case
diagram Sequence diagram Communication
diagram State machine diagram Activity
diagram Component diagram Deployment diagram
etc. Timing diagram
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2) Rules of the UML

• The UML has rules that specify how the building
  blocks can be put together in order to build a
  well-formed model
• A well-formed model is one that is semantically
  self-consistent and in harmony with all its
  related models
• The UML has semantic rules for -
• Names what we call things, relationships and
  diagrams
• Scope the context that gives specific meanings
  to names
• Visibility how those names can be seen and used
  by others
• Integrity how things properly and consistently
  relate to others
• Execution What it means to run or simulate a
  dynamic model

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3) Common mechanisms

• To make UML simpler
• Four types -
• Specifications
• Adornments
• Common divisions
• Extensibility mechanisms

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Example Modeling the Hello World program

• class HelloWorld
• public
• void greet()
• cout
• class HelloMalaysia public HelloWorld
• public
• void greeting()
• greet()
• cout

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Both classes can be represented graphically in
UML using the class building block, or class
diagram
Key abstraction for HelloWorld
greet() coutKey abstraction for HelloMalaysia
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The diagrams before are not complete as it does
not show the relationship between those classes
(if any). The relationship between those two
classes can be presented in another class
diagram, as shown below -
represents the generalization relationship
HelloMalaysia is a child (subclass) of HelloWorld
(superclass)
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UML 2.0 DIAGRAMS
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Tools

• The software tools that you can use to draw UML
  diagrams are -
• Rational Rose
• Visio
• Systems Architect
• VP-UML
• ArgoUML
• etc.