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Requirements& Estimating
Scotch on the RocksEdinburgh, March 3-4 2011
Peter BellRailo
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Agenda• Requirements
• Intent Driven Design
• User stories 201
• Estimation
• How much?
• Estimating scope
• Estimating duration
• Managing risk
• Four types of features
• Dealing with dark matter
• Managing commitments
• Fixed duration
• Fixed price
• Breaking the iron triangle
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Division of Labor
• My Job:
• Present ideas
• Your Job:
• Discriminate, select, adapt, experiment
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About you
• Consultant/in-house/product development?
• Team size?
• Number of projects/year?
• Agile?
• User stories?
• Estimates required?
• Fixed bid required?
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Requirements
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Before user stories . . .
What should we build?
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Intent Driven Design• Business intent
• Audiences
• Objectives
• User stories (tasks)
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User stories (1)• INVEST
• Independent
• Negotiable
• Valuable
• Estimable
• Small
• Testable
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User stories (2)• Tracer bullets, not tasks
• Splitting stories by ...
• Data
• Validation
• Paths
• Edge cases
• Isolate cross cutting concerns
• Make it work, then pretty/fast
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Estimation
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Why estimate?
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Why estimate?• Good reasons to estimate:
• Go/no go based on cost
• Market window
• ROI comparison
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Why estimate?• Good reasons to estimate:
• Go/no go based on cost
• Market window
• ROI comparison
• Bad reasons to estimate
• Because . . .
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Why estimate?• Good reasons to estimate:
• Go/no go based on cost
• Market window
• ROI comparison
• Bad reasons to estimate
• Because . . .
• Ask whether:
• Time, price or both?
• Will estimate matter?
• Accuracy required?
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Estimating scope• Ideal days (load factor)
• Story points
• 1,2,3,5,8
• 0?
• 10,20,30,51?
• T-shirt sizes
• Story count
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Estimating scope• Planning poker
• Keys:
• Delphi technique
• Independent estimates
• 1-3 hours, 1-3 sessions
• 2-6 people
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Estimating scope
• Magic/Affinity Estimating
• Large number of stories
• Experienced team
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Estimating time• Estimating velocity
• Historic rate
• Run iterations
• Make forecasts
• Burn down charts
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Managing risk
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Four types of feature• Rocket science
• Lab experiment
• New to you
• with a twist
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Dealing with dark matter• What you don’t know does hurt you ...
• But obviously . . .
• The dreaded API and technical risk
• Well, that’s almost right . . .
• Now that I see it . . .
• Mitigate:
• Set expectations
• Technical spikes
• Track and refine
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Making commitments
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Fixed duration• Optional features
• Team size
• Real options
• Schedule buffer
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Fixed price• Optional features
• Price buffer
• Scheduling flexibility?
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Breaking the iron triangle
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Breaking the iron triangle
Requirements are never fixed!
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Q&ATwitter: peterbellEmail: [email protected]• Requirements
• Intent Driven Design
• User stories 201
• Estimation
• How much?
• Estimating scope
• Estimating duration
• Managing risk
• Four types of features
• Dealing with dark matter
• Managing commitments
• Fixed duration
• Fixed price
• Breaking the iron triangle