Object Oriented System Design

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COS50-3 OOSD
INTRODUCTION TO OOSD (Week 1)
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AIMS AND OBJECTIVES

• To understand the software development process,
  including requirement specification, analysis,
  design, implementation and testing.
• To acquire various methodologies in software
  development,
• To understand the process of modelling real world
  problems and systems using UML,
• To develop skills on object oriented software
  development.

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EXPECTION AND EXAM

• Design solutions to complex problems
• Evaluate the significance of the object oriented
  paradigm in the production of complex software
• Appraise current and future technologies in their
  industrial context.
• Assignments and Exam
• -- Assignments 50
• -- Final exam (QuestionMark) 50

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TEACHING SCHEDULE

• Introduction outline OOSD, including the
  general process of software development, basic
  methodologies, preliminary on UML and Rational
  Rose.
• Use cases a useful tool for capturing
  requirements basic concepts of a use case,
  reasons for using use cases and how to apply it
  to capture user requirements.
• Analysis modelling management of a software
  process, analysis models, sequence diagram and
  CRC card.
• OO designing function oriented design, object
  oriented design and comparison, class diagram and
  statechart diagram
• Software patterns

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GOOD BOOKS

• Object-Oriented Software Engineering -- a use
  case driven approach (revised edition) by Ivar
  Jacobson
• UML Distilled (2nd Edition) by Martin Fowler
• Software Engineering (4th Edition) by Ian
  Sommerville
• Developing Applications with Java and UML by Paul
  R and Reed Jr
• An Introduction of Object Oriented Programming
  with Java (2nd Edition) by C Thomas Wu

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SOFTWARE PROCESS

• A software Process not just coding
• London Ambulance Service (LAS) -- a true disaster
  of software engineering.

• -- Time from early 1980s to 1992,
• -- Total cost 7.5 million,
• -- Result abandoned

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SOFTWARE PROCESS (Contd)

• LAS manual system

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SOFTWARE PROCESS (Contd)
LAS required system
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Auto Call Distributor
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SOFTWARE PROCESS (Contd)

• Things went wrong from very beginning
• -- End-user hostility -- lack of consultation,
• -- Official project issue report process was not
  followed,
• -- Problems were left in later stages, ignored
  and programmed,
• -- Hidden and newly introduced bugs,
• -- Test team had no knowledge about changes.
• Lessons was taught
• -- Software development is like other
  engineering processes,
• -- The process must be strictly followed.

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METHODOLOGIES

• Waterfall approach -- requirement, design, coding
  and test stages, one after another,
• Exploratory programming -- working system plus
  improvement,
• Prototyping -- establishing system requirements
  plus re-implementation,
• Formal transformation -- transforming
  specifications into program,
• System assembly from reusable components .

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WHATERFALL MODEL
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WHATERFALL MODEL (Contd)

• Requirement specification -- collecting and
  understanding clients requirements.
• Analysis -- establishing systems services,
  constraints and goals by consultation with
  systems users.
• Design -- establishing an overall system
  architecture, including program units and
  interface between those units,
• Implementation -- realising programs or program
  units and verifying that each unit meets its
  specification,

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WHATERFALL MODEL (Contd)

• integration -- integrating the individual program
  units are testing as a complete system to ensure
  the the system satisfy users requirements.
• Testing -- verification (Does the system work
  right?) and validation (Do we build up a right
  system?).

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WHATERFALL MODEL (Contd)
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CRISIS ARE STILL WITH US

• 31 of project will get cancelled before they
  ever get complete
• 88 of all projects are over schedule, over
  budget or both
• for every 100 projects started, there are 94
  restarts
• Average cost overun is 189 of original estimate
• Average time overun is 222 of original estimate

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CRISIS ARE STILL WITH US

• Causes
• -- Incomplete requirements -- 13
• -- Lack of user involvement -- 12.4
• -- Lack of resources -- 10.6
• -- Unreasonable expectations -- 9.9
• -- No management support -- 9.3
• -- Specification changes -- 8.7
• -- Lack of planning -- 8.1
• -- No longer needed -- 7.5
• Reason and solution
• -- Methodologies are difficult to follow
• -- Modelling language for implement the methods

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INTRODUCTION TO UML

• UML -- Unified Modelling Language
• It would help us (software engineers) to
  modelling real world problems and systems, e.g.
• -- Use Cases to capture requirements
• -- Analysis modelling to establish system
  specifications
• -- Design modelling to design a system
• -- Package large systems management

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INTRODUCTION TO UML

• It allows implementation-independent
  specification of
• -- user/system interactions (required behaviors)
• -- partitioning of responsibility (OO)
• -- integration with larger or existing systems
• -- data flow and dependency
• -- operation orderings (algorithms)
• -- concurrent operations

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CONTENTS OF UML

• Use cases,
• Interaction diagrams (Sequence Diagram, CRC,
  Collaboration Diagram)
• Class Diagram (aggregations, composites,
  interfaces and realisations)
• Package
• Activity Diagram
• State Diagram, State Chart, and Data Flow Diagram

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RATIONAL ROSE

• Rose is one of products from Rational Software.
• It is an expensive CASE (Computer-Aided Software
  Engineering) tool for object-oriented modeling.
• Based on UML (more or less).
• It provides semantics (a compiler) for UML.
• It has a reasonably intuitive GUI similar to
  standard drawing programs, like Illustrator, and
  is available for Windows and other platforms.
• It makes creating and maintaining your UML
  diagrams easier (or at least more consistent).
• Has many bizarre features, including generation
  of C (and other) code from your diagrams.

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RATIONAL ROSE (Contd)

• You can visit their website http//www.rational.c
  om/
• Getting the Evaluation copy (limited to 15 days)
• http//www.rational.com/tryit/rose/index.jsp
• Rational Rose is also Installed in our CIS Lab
  (Room 015)
• Our practicals will be based on the software.

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RATIONAL ROSE (Contd)

• Why do we need the Rational Rose? -- We use it to
  create a series of models for all the steps of
  OOSD
• -- Each model contains views, diagrams, and
  specifications to visualise and manipulate the
  elements in the model
• -- There are many views of each underlying
  element
• -- Every object in the design is represented
  once in the Rose model
• -- Rose maintains a consistent semantic
  representation in the model

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RATIONAL ROSE (Contd)

• What does Rational Rose look like?
• -- Standard toolbar
• -- Diagram toolbar
• -- Browser a drop-down list of things in your
  model
• -- Documentation window where you can add notes
  to a thing in your model
• -- Diagram windows where you draw your pictures
• -- Specifications
• -- Status bar

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SUMMARY

• Credit Scheme
• Software process
• Introduction of UML
• Introduction to Rational Rose