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Predicting Understandability of a Software Project Using COCOMO II Model Drivers. Ali Afzal Malik Barry Boehm A. Winsor Brown {alimalik, boehm, awbrown} @usc.edu 23 rd International Forum on COCOMO and Systems/Software Cost Modeling. Outline. Introduction Motivation & Related Work

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predicting understandability of a software project using cocomo ii model drivers

Predicting Understandability of a Software Project Using COCOMO II Model Drivers

Ali Afzal Malik

Barry Boehm

A. Winsor Brown

{alimalik, boehm, awbrown} @usc.edu

23rd International Forum on COCOMO and Systems/Software Cost Modeling

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outline
Outline
  • Introduction
  • Motivation & Related Work
  • Methodology
  • Results
  • Future Work
  • References

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introduction
Introduction
  • Understandability
    • “Degree of clarity of the purpose and requirements of a software system to the developers of that system at the end of the Inception phase”
  • Basic idea
    • Quantification enables prediction
    • Reuse inputs of software cost estimation
  • Empirical Study
    • Projects

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rup hump chart
RUP Hump Chart

(Kruchten, 2003)

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empirical study
Empirical Study
  • SE I (Fall) and SE II (Spring)
  • 2004 – 2007
  • 24 real-client, MS-student, team projects (SE I 2008, SE II 2008)
  • Process: MBASE/RUP (Boehm et al. 2005, Kruchten 2003)
  • Projects
    • Development-intensive
    • Used COCOMO II

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motivation related work
Motivation & Related Work
  • Some important considerations
    • 18% of software project failures due to unclear objectives and incomplete R&S (Standish Group 1995)
    • Escalation in cost of fixing requirements defects: rapid for large and considerable for smaller projects (Boehm 1981, Boehm and Turner 2004)
    • Requirement changes have significant impact on project’s budget and schedule (Zowghi and Nurmuliani 2002)

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motivation related work 2
Motivation & Related Work (2)
  • An objective mechanism to predict understandability enables
    • Minimization of resource wastage due to rework
    • Answering “How much RE is enough?”
  • Related previous work
    • “Expert COCOMO” (Madachy 1997)
      • Uses COCOMO II cost factors to quantify risk

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methodology
Methodology
  • Identified 8 relevant COCOMO II model drivers

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methodology 2
Methodology (2)
  • Weighted-sum formula
    • UNDR – understandability
    • MDi – ith Model Driver’s value
    • wi – weight of MDi
    • ni – nature of MDi; Є{-1, +1}
      • -1 for CPLX; +1 for the rest

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methodology 3
Methodology (3)
  • Model driver rating scale

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methodology 4
Methodology (4)
  • Voting for model driver weights
    • 22 students from SE II class
    • Rating scale
      • 1 (least important) – 5 (most important)

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methodology 5
Methodology (5)
  • Determine the lowest and highest numerical values of understandability

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methodology 6
Methodology (6)
  • min() and max()

min (MDi) {

if (ni = = +1) return minimum numerical value of MDi

else return maximum numerical value of MDi

}

max (MDi) {

if (ni = = +1) return maximum numerical value of MDi

else return minimum numerical value of MDi

}

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methodology 7
Methodology (7)

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methodology 8

VUA

ICA

WUA

2.86

44.12

85.38

126.64

UNDRLow

UNDRHigh

Methodology (8)
  • Project categories using UNDR ranges
    • Vaguely-understood applications (VUA)
    • Intermediate-clarity applications (ICA)
    • Well-understood applications (WUA)

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methodology 9
Methodology (9)
  • Ranges defining VUA, ICA, and WUA groups are adjustable
    • End-points of spectrum depend on weights
    • Range sizes can be non-uniform

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results
Results

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results 2
Results (2)
  • Prediction accuracy
    • ICA: 100%
    • VUA: 50% (2 out of 4)
    • WUA: 33% (1 out of 3)
    • Overall: 83% (20 out of 24)
  • Possible reasons for discrepancies
    • Inappropriate COCOMO II model drivers
    • Voters are different from developers
      • Projects # 5 & 22

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future work
Future Work
  • Weights for commercial projects using techniques such as Wideband Delphi (Boehm 1981)
  • Investigate other widely-used models e.g. SLIM (Putnam 1978) and PRICE-S (Freiman and Park 1979)
  • Analyze understandability’s contribution towards degree of requirements elaboration (Malik and Boehm 2008)

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references
References
  • Books
    • Boehm, B., Software Engineering Economics, Prentice-Hall, 1981.
    • Boehm, B., Abts, C., Brown, A., Chulani, S., Clark, B, Horowitz, E., Madachy, R., Reifer, D., and Steece, B., Software Cost Estimation with COCOMO II, Prentice Hall, 2000.
    • Boehm, B. and Turner, R., Balancing Agility and Discipline: A Guide for the Perplexed, Addison-Wesley, 2004.
    • Kruchten, P., The Rational Unified Process: An Introduction, Addison-Wesley, 2003.
  • Conference papers
    • Boehm, B., “Anchoring the Software Process”, IEEE Software 13(4), 1996, pages 73-82.
    • Freiman, F.R. and Park, R. E., “PRICE Software Model–Version 3: An Overview”, Proc. IEEE-PINY Workshop on Quantitative Software Models, 1979, pages 32-41.
    • Madachy, R., “Heuristic Risk Assessment Using Cost Factors”, IEEE Software4 (3), 1997, pages 51-59.
    • Malik, A. A. and Boehm, B., “An Empirical Study of Requirements Elaboration”, The 22nd Brazilian Symposium on Software Engineering (SBES’08), 2008.
    • Putnam, L. H., “A General Empirical Solution to the Macro Software Sizing and Estimating Problem”, IEEE Trans. Software Engr., 1978, pages 345–361.
    • Zowghi, D. and Nurmuliani, N., “A Study of the Impact of Requirements Volatility on Software Project Performance”, Proceedings of the Ninth Asia-Pacific Software Engineering Conference, 2002, pages 3-11.
  • Miscellaneous
    • Boehm, B., Klappholz, D., Colbert, E., et al., “Guidelines for Lean Model-Based (System) Architecting and Software Engineering (LeanMBASE)”, Center for Software Engineering, University of Southern California, 2005.
    • SE I (2008). Links to websites of all past semesters of Software Engineering I (CSCI 577A) course at USC, http://sunset.usc.edu/csse/courseroot/course_list.html#577a
    • SE II (2008). Links to websites of all past semesters of Software Engineering II (CSCI 577B) course at USC, http://sunset.usc.edu/csse/courseroot/course_list.html#577b
    • Standish Group (1995). “CHAOS”, http://www.standishgroup.com

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