Quality in Systems Development

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Quality in Systems Development
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• Questions to consider (in small groups)
• What makes good software?
• What makes good systems?
• How does one build high quality systems?
• Does extensive testing improve a systems quality?
• What is 'Quality'?

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Quality Management in Development Projects

• Quality is generally perceived as a technical
  issue but has a significant impact on project
  management
• Projects consist of tasks that add value by
  processing the projects product through a series
  of dependent tasks
• Any defect (human or machine) in one task is
  passed on to the next task, where it may be
  detected and add unscheduled time and effort

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Defect-Ripple
Task 1 passes input, which contains defects, to
task 2. These defects cause further defects to
occur in task 2. Task 2 passes input, which
contains defects, to task 3. These defects cause
further defects to occur in task 2. The cost of
repair rises at an exponential rate!
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Defect-Ripple

• Each subsequent task is seen to have been under
  estimated.
• Phased-end reviews will not be able to detect all
  the accumulated defects
• Without quality assurance, a major cause of the
  difference between estimated effort and actual
  effort is the defect ripple effect
• Accounts for up to 40 of total effort of a
  project over its development cycle (Caper Jones)

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• Defect-Ripple
• It is imperative that defects
• be prevented from occurring
• and, if they do, they need to be identified and
  corrected as soon as possible.

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Definition of Quality

• The quality of a product acceptable to a client
  is highly dependent upon the client themselves.
• Quality Conformance to Requirements
• What makes good software?
• What makes good systems?
• What does conformance to requirements mean?

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Conformance to Requirements

• Functionality -What the system must be capable of
  doing
• Output - What the system must produce.
• Performance - The type of equipment must it
  operate on The volumes of data it must handle and
  the transaction rate required
• Reliability - The consequences of failure, and
  how often can failure be accommodated
• Maintainability - How easy is it to alter the
  system?
• Security - How well must its value be protected.
• Operability - How easy is the system to operate.

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Conformance to Requirements

• Cost - What is affordable to the client
• Efficiency - How effectively does it use
  resources.
• Interoperability - How it interfaces with other
  systems.
• Portability - How difficult it is to move to a
  different environment
• Reusability - Ease of reuse of parts of the system

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Quality Criteria

• Each quality attribute has a subset of criteria
• Functionality
• Completeness (is all the data and function
  present)
• correctness (is the data and function defect
  free)
• traceability (can the data and function be
  tracked from requirements, through design and
  into production)
• Some attributes are potentially incompatible eg.
  security and response time, or usability and
  efficiency

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Measuring Quality

• The measure of quality is the cost of
  nonconformance
• Price of Noncompliance
• It is anything which causes the system not to
  perform as required
• Loss of income because system does not work
  correctly
• Time and effort to locate and fix errors
• Damages to a medical client as result of
  incorrect data or diagnosis using information
  system

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The Future Without Good Quality Management
At some point maintenance uses more of the budget
than is available. Repairs to existing software
introduce problems as quickly as they are
corrected.
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The Future with Good Quality Management
Money spent on quality programs not only reduce
errors in new code, but in the repairs and their
repairs as well!
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Cost of Quality

• Cost of Quality is equal to
• the Price of Conformance plus
• the Price of Non-Conformance

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Cost of Quality

• Price of Conformance
• Inspections
• Setting and Implementing Standards
• Training
• Measuring
• anything done to assure quality
• Price of Non-Conformance
• Cost of repairs and damages
• Loss of time, income
• cost of anything which is a result of non
  conformance

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Two Philosophies

• Appraisal Test and repair errors in product
• Prevention Identify root cause of error, fix
  error and its cause
• Appraisal
• Based on early ideas derived from manufacturing
  practice
• Same error keeps being repeated, so fault recurs

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Appraisal
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Appraisal

• Assumes that 100 quality is not achievable
  because the price of conformance would be too
  high
• Cost of fixing error small, but the repair is
  required many times in the life of the system
• Quality improvements come through innovation (but
  this is not reliable)

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Prevention

• Assumes prevention is better than repeated cure
• Correct error
• Look for similar problems
• Identify and fix cause
• High initial cost to repair error, but the
  problem does not repeat.

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Prevention
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Quality Management

• In the past, poor quality blamed on workers
• Responsibility has shifted to management.
• Components of Total Quality Management
• Quality Environment
• Quality Assurance
• Quality Control
• Necessary to manage these to achieve quality

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Quality Environment

• Culture and Infrastructure proved to achieve high
  quality
• Commitment must be real
• Responsibility for senior management to create
  enable

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Quality Assurance

• Middle management task
• Must do things right the first time
• Set standards
• Provide training
• Define methods and deliverables
• Provide the correct tools
• Assign tasks to those with the skills
• Define prevention procedures

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Quality Control

• Operational level activity
• Final step to catch quality problems
• Includes Inspections, Testing, Fixing problems

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A Process Model of Quality

• The output must conform to requirements but the
  inputs must also!
• The process is a customer to the supplier.

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Quality Improvement

• Techniques to implement quality improvement
• Use a well defined lifecycle
• Define tasks and deliverables
• Set quality standards for all deliverables
• Encourage informal walkthroughs
• Use formal walkthroughs
• Perform code inspections.

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Quality Improvement

• Techniques to implement quality improvement
• Reviews and audits of deliverables
• Give rewards for quality
• Use defect seeding
• Provide training and mentoring
• Separate duties

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• The system of quality is prevention.
• The quality standard is zero defects.
• Note zero defects means no deviation from
  requirements. Eg. No more than one crash per six
  months