Barry Boehm

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COPLIMO A Software Product Line Life Cycle Cost
Estimation Model
Barry Boehm
CS510, Fall 2005
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Outline

• Background
• Constructive Product Line Investment Model
  (COPLIMO)
• The product line development cost model
• The annualized post-development life cycle
  extension
• Conclusions

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Background

• Benefits vs. Costs of product line
• Does product line pay?
• Traditional product line cost estimation models
  mostly underestimate the ROI for product lines by
  focusing only on development savings
• Apply RCWR surcharge to entire product not only
  to the reused portions
• If life cycle costs are considered, high payoff
  comes from a smaller code base to undergo
  maintenance
• COPLIMO life cycle model addresses the
  shortfalls, and helps to
• Determine whether it pays to develop software
  product as a product line
• Estimate how many members of the product line
  family will be developed
• Compare ROIs from different scoping of a product
  line

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Outline

• Background
• Constructive Product Line Investment Model
  (COPLIMO)
• The product line development cost model
• The annualized post-development maintenance cost
  model
• Conclusions

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COPLIMO Model Overview

• Based on COCOMO II software cost model
• Statistically calibrated to 161 projects,
  representing 18 diverse organizations
• Based on standard software reuse economic terms
• RCWR Relative Cost of Writing for Reuse
• RCR Relative Cost of Reuse
• Avoids investment overestimation, savings
  underestimation
• Avoids RCWR for non-reused components
• Includes savings from smaller life-cycle code
  base
• Provides experience-based default parameter
  values
• Simple Excel spreadsheet model
• Easy to modify, extend, interoperate

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COPLIMO - RCWR

• Development for Reuse (RUSE)
• In COCOMO II Database, 11 out of 161 projects
  rated as VH for RUSE, and 1 rated as XH
• Productivity range of 1.24/0.95 1.31
• And two other contributing variables
• Required Reliability (RELY)
• At least Nominal for Nominal and High RUSE
  ratings,
• At least High for Very High and Extra High RUSE
  ratings
• Degree of Documentation (DOCU)

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COPLIMO RCWR (Cont.)

• Required Reliability (RELY)
• Constraints At least Nominal for Nominal and
  High RUSE ratings, at least High for Very High
  and Extra High RUSE ratings
• Degree of Documentation (DOCU)
• Constraint No more than one level below the RUSE
  rating

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COPLIMO RCR

• Reused, or Black Box (unmodified code) RCR model
• Assessment and
• Assimilation (AA) factor
• Adapted, or White Box (modified code) RCR model
• AA
• Non-Linear Model

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Guidelines for Quantifying Adapted Software
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Outline

• Background
• Constructive Product Line Investment Model
  (COPLIMO)
• The Basic product line development cost model
• The annualized post-development life cycle
  extension
• Conclusions

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Basic COPLIMO Development Cost Model (1)

• Simplifying assumptions about uniformity and
  stability
• Every product roughly the same size (PSIZE)
• Roughly the same fractions of product-specific
  (PFRAC), adapted (AFRAC), and reused (RFRAC)
  software
• Inputs and outputs

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Basic COPLIMO Development Cost Model (2)

• RCWR
• RCWR RUSE DOCU RELY
• 1 product development effort
• Non-PL Effort for developing N similar products
• PMNR (N) N ? A? (PSIZE)B ? ? (EM)
• Where PSIZE is the general software product size,
  A and B are the COCOMO II calibration coefficient
  and scale factor, and ? (EM) is the product of
  the effort multipliers for the COCOMO II cost
  drivers
• PL Effort (the first product)
• PMR (1) PMNR (1) PFRAC RCWR(AFRACRFRAC)
• Note RCWR not applied to non-reused portion,
  where many other models overestimate RCWR

• RCR parameters

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Basic COPLIMO Development Cost Model (3)

• Determining RCR
• Equiv. size of product- specific portion
• Equiv. size of reused portion
• Equiv. size of adapted portion
• Total EKSLOC
• Effort
• ROI (PL Effort Savings for K products - PL
  Reuse Investment) / PL Reuse Investment

PMR (N) N ? A? (EKSIZE)B ? ? (EM)
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Outline

• Background
• Constructive Product Line Investment Model
  (COPLIMO)
• The product line development cost model
• The annualized post-development life cycle
  extension
• Conclusions

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Basic COPLIMO Annualized Life Cycle Cost Model

• Annual Change Traffic (ACT)
• relative fraction of a products software that is
  modified per year

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Basic COPLIMO Annualized Life Cycle Cost Model
(1)

• Annual Change Traffic (ACT)
• Relative fraction of a products software that is
  modified per year
• Life cycle effort without reuse
• Annual maintained software
• L times maintenance effort
• Life cycle effort with reuse
• Three categories of annual maintenance and AMSIZE

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Conclusions

• Software product line payoffs are significant
• Especially across life cycle
• Less code to maintain
• Cost models and business case analysis enable
  assessment of situation-dependencies
• Lead to better product line decisions
• COPLIMO avoids investment overestimation, savings
  underestimation
• Further extensions feasible