The Art and Science of Estimating Software Development Cost

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The Art and Science of Estimating Software
Development Cost

• Glenn Briskin
• Partner, Sierra Systems Group
• A. Nicklas Malik
• Technical Architect
• Certified Function Point Specialist

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Agenda

• Sierra Systems Intro
• Estimating Software Development
• Project Management Point of View
• Key concepts for creating and managing estimates
• Technical Architect Point of View
• Estimating Size (using Function Points)
• Estimating Cost (using Historical Data)

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Sierra Systems Intro

• A full service systems integration company
• Emphasis on business solutions
• Over 900 consultants, 300 in PNW
• Vancouver and Victoria
• Bellevue and Olympia
• Olympia office since 2000 serving over 25 state
  agencies
• EGovernment, Health, Justice, Enterprise
  Solutions
• Strong methodology and technology expertise

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Managing Estimates

• Whats an estimate?
• What goes into an estimate?
• What happens once you make an estimate?
• How can you make it work for you, not against you?

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Whats an Estimate?

• An estimate predicts what something will cost and
  how long it will take to deliver
• Numbers
• Confidence Level

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What goes into an Estimate?

• Your understanding about what you want
• Your experience in doing that before
• The more you know about each, the easier it will
  be to estimate

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Understanding and Experience

• Understanding
• What problem will be solved? (Objectives)
• What capabilities will solve it? (Functionality)
• How will you do it? (Tasks)
• What assumptions and constraints do you have?

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Understanding and Experience

• Experience
• What has it taken for you or others to do this?
• What historical information do you have?
• What expert experience can you draw on?
• What is your confidence level in the
  applicability of your information?
• What do you know about your possible resources?

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Estimating Process
Estimates of Costs and Time
Functionality
Estimating Tools and Processes
Tasks/Resources
Confidence Level
History
Assumptions and Constraints
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How much of this comprises your estimate?
Functionality
Estimating Tools and Processes
Estimates of Costs and Time
Tasks/Resources
Confidence Level
History
Assumptions and Constraints
All of it!
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What Happens when you make an Estimate?

• Set expectations
• Cost, Time, Scope
• People see what they are looking for
• Create a baseline
• Cost, Time, Scope
• Assumptions, Constraints, Confidence

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Making the Estimate Work for You

• When any part of the estimate changes
• Functionality
• Tasks
• Assumptions/Constraints
• Cost and Time Estimates
• Confidence Level
• Then the entire estimate has changed
• Adjust expectations and show variance to the
  baseline
• Negotiate changes to expectations

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Estimating Models A case for Function Points
Estimating Tools and Processes

• And then magic happens
• Your inputs vary in quality and completeness
• Characteristics of a useful estimating model
• Consistently applied to the information available
• Usable early with accuracy
• Easily updateable responsive to changes
• Applicable to historical projects
• Adjustable with experience

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Top down vs. Bottom Up
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Top-down Cost Estimation

• First estimate the size.
• Count function points.
• Estimate total lines of code (KLOC)
• Apply Measured Productivity
• Hours / Function Point or Hours / KLOC
• Calibrate using local history or industry
  averages
• Cost size productivity

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Ease into measurement

• On a couple of projects, count the function
  points at the beginning, and at every major
  release.
• At each point, take the effort expended and
  calculate productivity (hours per function point
  delivered).
• Store for future use in estimating.

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Other benefits of measurement

• Measurement can lead to improving
• Cost performance
• Methodology
• Client Satisfaction
• Credibility
• The more weknow, the betterwe can do.

Time
Scope
Plan
Tasks
People
Functions
Quality
Features
Goals
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Any measurement should be

• Simple
• Consistent
• Not technology or platform dependent
• Not company dependent
• Useful at different points in software lifecycle

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The generic application
Application
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Relative Difficulty

• Each function gets a number of points
  reflecting how hard the function is to write.
  
• Each of these five functions can be complex,
  average, or simple.
• To be consistent, there is a whole set of rules
  to decide what function to use, and what level of
  complexity to measure it as.

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Complexity

• Depending on requirements, some systems are
  harder to write that needs to be taken into
  account.
• Complexity factors are multiplied against the
  total of the function points causes the final
  number to range from 65 to 135

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Demo Counting Tool

• Excel spreadsheet
• Pages for types of files (ILF, EIF)
• One page for all transaction types (EI, EO, EQ)
• Summary and Productivity pages
• Record of counter notes, constraints, use case
  notes, data dictionary, any other pertinent
  information

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Estimating Cost

• Start with a size measurement
• Multiply by productivity
• Dependent on platform, language, environment (IT
  shop vs. Outsource), project requirements
  (documentation, reviews, testing), etc.
• Heavily dependent on historical performance

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Demo Productivity Calculations

• Guidance on what industry or local averages are.
• Room for applying variances to averages
  justifications
• Calculations by Rational Unified Process Workflow

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Summary

• Measure size using simpleconstructs, easy to
  understand
• Multiply size by productivity
• Requires measurement of pastprojects to
  calibrate productivity
• As requirements improve, estimates improve

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Software Estimation Resources

• International Function Point Users Group (
  www.ifpug.org )
• Certification
• Counting Practices Manual
• Software Assessments, Benchmarks and Best
  Practices by Capers Jones
• Software Cost Estimation with COCOMO2by Barry
  Boehm, et. al.

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Where to Get More Information

• Glenn Briskin
• Partner, Sierra Systems Group
• 360 570 4531
• GlennBriskin_at_SierraSystems.com
• A. Nicklas Malik
• Technical Architect
• Certified Function Point Specialist
• 360 570 4546
• NickMalik_at_SierraSystems.com