Cmpe 589

1
Cmpe 589

• Spring 2006
• Lecture 2

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Software Engineering

• Definition
• A strategy for producing high quality software.

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Software Engineering

• Definition Of High Quality Software
• It must be useful (to the original customer).
• It must be portable (work at all of the
  customers sites).
• It must be maintainable.
• It must be reliable.
• It must have integrity (produces correct results,
  with a high degree of accuracy).
• It must be efficient.
• It must have consistency of function (it does
  what the user would, reasonably expect it to do).
  
• It must be accessible (to the user).
• It must have good human engineering (easy to
  learn and easy to use).

4
Software Development Models

• Systems Approach
• Definition of a system (a collection of
  things)
• A set of entities.
• A set of activities.
• Descriptions of entity relationships.
• System boundaries.
• Distinguish between activities (processes,
  methods) and objects (data).
• Determine the relationships between the objects.

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Software Development Models

• Advantages Of Bounded Systems
• Makes problem identification easier.
• (It is often useful to think of a system as a
  sub-system, for the purpose of extension).

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Software Development Models

• Software Engineering Approach
• The art of producing systems involves the craft
  of programming.
• Fabricating software using "off the shelf"
  components.
• Why Doesnt This Work Well
• Customers are not capable of describing their
  needs completely or precisely.
• Customers change the specifications.

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Software Lifecycle Models

• Phases
• Requirements, analysis, and design phase.
• System design phase.
• Program design phase.
• Program implementation phase.
• Unit testing phase.
• Integration testing phase.
• System testing phase.
• System delivery phase.
• System delivery.
• Maintenance.

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Software Lifecycle Models

• Waterfall Model
• Errors require at least one step back in the
  cycle.
• Change Failure.

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Software Lifecycle Models

• Rapid Prototyping Model
• Start with user interface (probably most
  important to customer).
• When customer is happy with that, then work on
  the behind the scenes stuff.
• Customer is involved throughout the entire
  process.

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Software Lifecycle Models

• Spiral Model
• Prototyping is used to reduce risk.

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Software Lifecycle Models

• Fourth Generation Techniques
• (Usually a tool that generates the code, through
  the use of a graphical interface).
• Non-procedural data-base query languages.
• Some type of report generator.
• Often capable of high-level graphics.
• Spreadsheets.

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Capability Maturity Model

• (A Strategy For Improving The Software Process).
• Maturity Models
• Level One Initial Process
• Ad-hoc approach to software design.
• Inputs are ill defined.
• Outputs are expected (transitions not defined or
  controllable).

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Capability Maturity Model

• Level Two Repeatable Process
• Requirements are input.
• Code output.
• Constraints - budget time.
• Metrics - project related
• Software size.
• Personnel effort.
• Requirement validity.
• Employee turnover.

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Capability Maturity Model

• Level Three Defined Process
• The activities of the process have clearly
  defined entry exit conditions.
• Intermediate products - well defined and easily
  visible.
• Metrics
• Requirements complexity.
• Code complexity.
• Failures discovered.
• Code defects discovered.
• Product defect density.
• Pages of documentation.

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Capability Maturity Model

• Level Four Managed Process
• Information from early process activities can be
  used to schedule later process activities.
• Metrics
• Defined and analyzed to suit the development
  organization.
• Data
• Process type.
• Producer reuse.
• Consumer reuse.
• Defect identification mechanism.
• Defect density - model for testing.
• Configuration management scheme.
• Module completion rates over time.

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Capability Maturity Model

• Level Five Optimizing Processes
• Measures from activities are used to improve
  processes.

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Capability Maturity Model

• How Are Metrics Used?
• Assess the process level.
• Determine metrics to use.
• Recommend metrics, tools, techniques.
• Estimate project costs and schedule.
• Collect metrics at the appropriate level.
• Construct a project database.
• Evaluate cost and schedule.
• Evaluate productivity and quality.
• Form a basis for future estimates.

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Capability Maturity Model

• Benefits Of Process Maturity And Metrics
• Enhanced understanding of the process.
• Increased control over the process.
• Clear migration path to a more mature process.
• More accurate estimates of cost and scheduling of
  staff.
• More objective evaluation of changes needed
  (techniques, tools, methods, ect.).
• More accurate estimation of changes on project
  cost and schedule.