Software%20Engineering

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Software Engineering

• A Preview
• Chapter 1

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Outline

• My Background
• Definitions of software engineering (SE)
• Historical origins of SE
• SE as part of systems engineering
• SE consists of many activities in addition to
  programming
• SE and other disciplines

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My Background

• BSc in computer science from Ontario
• MSc and PhD in computer science at UofR
• Research specializing in machine learning and
  game theory
• Avid programmer. First language was Basic in
  1989, last was C 8 months ago ?.

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Industry Experience

• Government of Ontario (Web developer)
• IBM Canada (lead developer of e-commerce site)
• Dundee Securities (network security analyst)
• Sask. Watershed Authority (team lead)
• UofR (programmer analyst I, II)
• Numerous lab teaching and lecturing appointments

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Definitions

• The application of engineering to software
• Field of computer science dealing with software
  systems
• large and complex
• built by teams
• exist in many versions
• last many years
• undergo changes

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Definitions

• Application of a systematic, disciplined,
  quantifiable approach to the development,
  operation, and maintenance of software (IEEE
  1990)
• Multi-person construction of multi-version
  software (Parnas 1978)

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Role of SE in system design

• SE part of larger projects
• Embedded
• Software requirements to be balanced against
  others
• e.g., telephone switching systems
• certain requirements can only be met by hw, sw,
  and special devices

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History

• The field of software engineering was born in
  1968 in response to chronic failures of large
  software projects to meet schedule and budget
  constraints
• Recognition of "the software crisis"
• Term became popular after NATO Conference in
  Garmisch Partenkirchen (Germany), 1968

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Role of software engineer

• Programming skill not enough
• Software engineering involves "programming-in-the
  large"
• understand requirements and write specifications
• derive models and reason about them
• master software
• operate at various abstraction levels
• member of a team
• communication skills
• management skills

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The software lifecycle (a preview)
waterfall model
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Relationships between SE and other CS disciplines

• Programming languages
• Operating systems
• Data bases
• Artificial intelligence
• Theory
• Management science
• Systems engineering
• Others

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Programming

• Languages are the central tools used in software
  development.
• Modularity
• Separation of implementation and specification
• Java and packages
• Exception handling
• Engineer support for error checking

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Operating Systems

• The first large software systems built.
• Concepts developed in OS are applicable to many
  large-scale software systems
• Virtual machines, abstraction, separation of
  policy from mechanism
• Separate the what from the how

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Databases

• Concept of data independence
• Another ex. of separation of specification and
  implementation.
• Many innovations in database technology were
  required with the design of large-scale software
  systems
• Storing large structured or unstructured objects.
• Transaction lengths.

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Artificial Intelligence

• Many are large-scale software systems.
• Necessity of exploratory development since many
  of them were vague on how they worked.
• SE techniques used in expert systems, a
  modularized system with clear separation between
  facts known and rules used to process facts.
• Programming assistants.

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Theoretical Models

• Many models have been developed that have become
  useful tools in SE
• Finite State Machines
• Basis of software specifications and a model for
  software design and structure.
• Petri Nets
• Originally used to model hardware, but have been
  adopted to model software.

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Topics covered in this course

• Part I SE Overview
• SE Introduction
• Software Qualities and Principles
• Software Design and Architecture
• Part II Specification Testing
• Operational and Descriptive specifications
• Part III Software Production Process
• Activities and models

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Group project

• Comprehensive project that covers major
  deliverables and duties of a real developer team.
• Groups of 4 should be decided by the end of the
  week.
• All members of team receive same project mark
• Tip Pick a well-rounded group of writers,
  testers, and developers.

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Group project

• Each group will meet with me at least once midway
  through to discuss project.
• I will provide a list of available projects, but
  Im also open to ones not on a list if I think
  they are viable.
• REMEMBER You have 6.5 weeks to finish it,
  starting now!

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CHAOS Report by Standish Group for 1995

• Standish Group studied 3682 projects in 365
  companies in 1995
• Huge investment in software development
• US 250 billion spent each year on IT development
  of c. 175 000 projects in the US (1995 estimates)
• Huge losses
• US 81 billion spent on cancelled projects and
  additional 59 billion on time overruns by US
  companies and government (1995estimates)

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• Project success rate
• Success 16.2
• Challenged (either late or over budget) 52.7
• Impaired (cancelled) 31.1
• Average cost overrun of original estimate was
  189
• Average time overrun of original estimate was
  222
• On average only 61 of originally specified
  features and functions were available on these
  projects

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Challenges of Software Development

• Productivity
• Growing demand for new systems and variants
• Complexity
• Requirements concerning functionality,
  efficiency, and especially connectivity are
  constantly growing.
• Quality
• User expectations of quality are high, and may be
  life critical
• Maintenance Legacy Systems
• 20 years or more

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Programming vs. Software Engineering

• Small project
• You
• Build what you want
• One product
• Few sequential changes
• Short-lived
• Cheap
• Small consequences

• Huge project
• Teams
• Build what they want
• Family of products
• Many parallel changes
• Long-lived
• Costly
• Large consequences

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Average cost of software
Object-Oriented and Classical Software Engineer
5th Edition, Schach (2002)