From Flow Charts to UML 3

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From Flow Charts to UML - 3
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Object Orientation

• Object - any thing on which we store data,
  together with the operations that are used to
  alter that data
• Object class - the type of object. E.g.
  Insurance claim might a an object class
• Instance - a particular object of a class. E.g.
  Motor Claim and Flood Damage Claim are both
  instances of Insurance Claim
• Encapsulation - packaging the data and the
  operations

See Curtis and Cobham Ch 16, Yeates Cadle Ch 4
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Object Orientation
Object Class
Instances
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Object Orientation
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Object Orientation

• Benefits
• Produces modules which are easily amended
• A store of reuseable code
• Repositories of defined classes
• It is claimed that
• an object type is inseparable from the operations
  in which it participates
• the Unified Modelling Language (UML) is a more
  natural way of viewing the world

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From Analysis to Design

• Analysis will have developed a logical model of
  the system
• Design phase is the transition from what is
  required to how the requirements will be achieved
• Three possible problem areas
• 1. New requirements
• Processes (new DFDs)
• Information needed (Entities)
• 2. Inefficiencies of the existing system
• 3. Physical aspects may have been included
• Revision of logical model
• new DFDs

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From Analysis to Design

• Logical design

Project Repository
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From Analysis to Design

• Alternative design suggestions, before
• detailed physical design, including
• hardware specifications
• database or file specifications
• program specifications
• input / output specifications
• identification of procedures surrounding the
  system
• implementation schedules

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From Analysis to Design

• Physical design

Project Repository
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Combining Analysis and Design

• OOAD
• Use-case diagram
• -interaction between external actors and actions
  performed within a system
• Class and Object diagrams
• -static structure of objects in the problem
  domain
• State diagrams
• -capture the dynamic state transitions of an
  object
• Sequence diagrams
• -shows the passing of messages between objects,
  i.e. the interaction which causes functions to
  happen

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Combining Analysis and Design

• Object Orientation and Design (OOAD)
• Rapid Application Development (RAD)
• Cost and competitive pressures on businesses
• Traditional structured systems development may be
  too slow
• OOAD and RAD both have
• strong focus on the business situation
• extensive use of parallel development activities
• re-use of previously developed system components
• blend analysis and design steps

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Combining Analysis and Design

• Which diagrams relate to analysis, and which to
  design?
• ALL
• process of refinement

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Combining Analysis and Design

• RAD
• general strategy of developing information
  systems
• goals
• rapidly analyse a business problem
• intense co-operation between users and developers
• fast delivery of systems
• emphasis on prototyping
• extensive use of CASE (Computer Aided Software
  Engineering) tools to generate code and hold
  templates

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Combining Analysis and Design

• 4 pillars of RAD (James Martin, 1991)
• Tools
• Methodology
• People
• Management

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Combining Analysis and Design

• Methodology

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Combining Analysis and Design

• People
• developers must be trained in using tools and
  co-operating with users
• experience often gained through working in a RAD
  cell
• Management
• must be aware of RAD techniques
• must be totally supportive of the process
• must facilitate problem solving and decision
  making

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Combining Analysis and Design

• RAD advantages and disadvantages
• Fast
• Cheaper - fewer resources involved
• Closer to current business needs
• BUT
• is it possible to have
• speed AND (low) cost AND (high) quality?

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End of Lecture