PROJECT MILESTONES

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PROJECT MILESTONES
Group Presentations 5 mins presentations
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Introduction to Software Engineering
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What is Software Engineering?

• Software?
• Websters Dictionary the entire set of
  programs, procedures, and related documents
  associated with a system
• Engineering?
• Websters Dictionary The practical applications
  of scientific and mathematical principles

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What is Software Engineering?

• SE is a discipline whose aim is the production of
  fault-free software, on time, within budget, that
  satisfies the users needs.

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Scope of Software Engineering

• Scope of SE is extremely broad
• Historical aspects
• Economic aspects
• Maintenance aspects
• Specification and Design aspects
• Team Programming aspects

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Historical Aspects

• The Term Software Engineering first used at the
  1968 NATO conference
• Aim to solve the Software Crisis
• Software Crisis low quality, over budget, and
  late.
• Software Engineering Versus other Engineering
  fields.

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Historical Aspects cont.

• building bridges vs operating systems?
• Bridge collapse vs OS crash
• perfect engineering vs fault tolerance
• Complexity
• bridges are analog. Described by continuous
  mathematics.
• software systems are discrete. The total number
  of all possible states can be vast.
• Some not considered by developer

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Historical Aspects cont.

• Maintenance
• software maintenance is much more complex
• Corrective maintenance
• Enhancement maintenance
• SE is fairly new (25 years)

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Economic Aspects

• Software Engineering Versus Computer Science
• Computer scientist investigate all solution to a
  problem
• Software engineer interested only in those
  solutions that make sound economic sense.
• short term effects Versus long term effects
• Phases of the Software Life Cycle

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Maintenance Aspects

• Phases of Life Cycle
• Requirements
• Specifications
• Design
• Implementation
• Integration
• Maintenance
• Retirement
• Cost of all phases must be taken into account

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Maintenance Aspects Cont.

• Maintenance is a very costly phase
• Fig. 1.2 Maintenance constitutes 67 of total
  cost
• Good software is maintained--Bad software is
  discarded
• Different types of maintenance
• corrective maintenance 20
• enhancement
• adaptive maintenance 20
• perfective maintenance 60

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Specification and Design Phase

• Errors exist
• Better to fix errors during earlier phases
• cost increases very sharply (see Fig 1.4 1.5)
• 60 to 70 of faults are specification and design
  faults
• need new techniques to avoid errors during Spec.
  and Design phases.

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Team Programming Aspects

• Hardware cheap -- can build products too large to
  be built by one person in available time.
• Team projects
• Interface problems
• Communication Meetings/conferencing
• Team Organization
• Suppose a product takes 1 programmer 1 year
• Generally, itd take a group of 4 programmers
  more than 3 months

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Structured Vs. Object-Oriented Paradigms

• Structured paradigm (1975-1985)
• structured systems analysis, design, programming,
  testing
• had great success initially
• Started to fail with larger products (gt50,000
  LOC). Did not SCALE UP.
• Reason either action oriented or data oriented
  but not both.

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Object-Oriented Paradigm

• Both data and actions are of equal importance
• Object Software component that incorporates both
  data and the actions performed on that data.
• Example
• Bank account
• data account balance
• actions deposit, withdraw, determine
  balance

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OO Paradigm Cont.

• Object-Oriented paradigm(see Fig. 1.6)
• Encapsulation actions done on an object are
  implemented within that object
• gt conceptual independence
• gt independence of effects
• Information hiding implementation details are
  hidden from outside the object
• gt reduce the level of complexity
• gt Maintenance less costly
• gt Object reuse

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Transition from Analysis to Design

• Structured paradigm
• Analysis
• determine what product is to do
• Design
• architectural design project is broken into
  modules
• Detailed design each module is designed (data
  structures and algorithm for each module)
• Transition is too sharp

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Transition from Analysis to Design

• OO paradigm
• Object-Oriented Analysis
• determine what the product is to do
• extract the objects
• Object-Oriented design
• detailed design of the objects
• Objects enter the Life Cycle at early stage