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CSE360 Lecture 27

CSE360 Lecture 27

Introduction to Software Engineering
Software Cost Estimation
(201807)

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  1. CSE360
    Introduction to Software Engineering
    Lecture 27:
    Software Cost Estimation
    Javier Gonzalez-Sanchez
    [email protected]
    javiergs.engineering.asu.edu
    Office Hours: By appointment

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  2. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 2
    Software Cost Estimation Methods
    • Cost estimation: prediction of both the person-effort
    and elapsed time of a project
    • Methods: Algorithmic, Expert judgement, Estimation by
    analogy, Parkinsonian (Parkinson’s Law).
    “work expands so
    as to fill the time available for its completion”
    • Best approach is a combination of methods: compare
    and iterate estimates, reconcile differences

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  3. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 3
    COCOMO Model
    • The Constructive Cost Model (COCOMO) is a
    procedural software cost estimation
    model developed by Barry W. Boehm.
    • The model parameters are derived from fitting
    a regression formula using data from historical
    projects (61 projects for COCOMO 81 and 163
    projects for COCOMO II).
    • COCOMO is the most widely used, thoroughly
    documented and calibrated cost model

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  4. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 4
    COCOMO II
    COCOMO II
    product size estimate
    product, process,
    platform, and personnel
    attributes
    reuse, maintenance,
    and increment parameters
    organizational
    project data
    development, maintenance
    cost and schedule estimates
    cost, schedule distribution by
    phase, activity, increment
    recalibration to
    organizational data

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  5. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 5
    COCOMO II
    There is an online implementation here:
    http://csse.usc.edu/tools/COCOMOII.php

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  6. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 6
    COCOMO II - User Interface

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  7. COCOMO
    Outputs

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  8. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 8
    COCOMO II - Output Result A

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  9. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 9
    COCOMO II - Output Result B

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  10. COCOMO
    Size and Scale Drivers

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  11. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 11
    COCOMO II - Inputs

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  12. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 12
    Size
    • The size of a software system can only be known accurately
    when it is finished.
    • As the development process progresses then the size estimate
    becomes more accurate.
    • Several factors influence the final size
    o Use of reused systems and components;
    o Programming language;
    o Distribution of system.
    • Effort for adapted software (reused or modified)
    is not the same as for new software.
    • Approach: convert adapted software into equivalent size of
    new software.

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  13. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 13
    Nonlinear Reuse Effects
    • The reuse cost function does not go through the origin due to a cost of
    about 5% for assessing, selecting, and assimilating the reusable
    component.
    • Small modifications generate disproportionately large costs primarily
    due the cost of understanding the software to be modified, and the
    relative cost of interface checking.
    Relative
    cost
    Amount Modified
    1.0
    0.75
    0.5
    0.25
    0.25 0.5 0.75 1.0
    0.55
    0.70
    1.0
    0.046
    Usual Linear
    Assumption
    Data on 2954
    NASA modules
    [Selby,1988]

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  14. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 14
    COCOMO II - Inputs

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  15. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 15
    Scale Drivers
    1. Precedentedness (PREC). Degree to which system is
    new and past experience applies
    2. Development Flexibility (FLEX). Need to conform with
    specified requirements
    3. Architecture/Risk Resolution (RESL). Degree of design
    thoroughness and risk elimination
    4. Team Cohesion (TEAM). Need to synchronize
    stakeholders and minimize conflict
    5. Process Maturity (PMAT). SEI CMM process maturity
    rating
    ©USC-CSSE 15

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  16. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 16
    Scale Drivers Rating
    Scale Factors (Wi
    ) Very Low Low Nominal High Very High Extra High
    Precedentedness
    (PREC)
    thoroughly
    unprecedented
    largely
    unprecedented
    somewhat
    unprecedented
    generally
    familiar
    largely
    familiar
    throughly
    familiar
    Development
    Flexibility (FLEX)
    rigorous occasional
    relaxation
    some
    relaxation
    general
    conformity
    some
    conformity
    general
    goals
    Architecture/Risk
    Resolution (RESL)*
    little (20%) some (40%) often (60%) generally
    (75%)
    mostly
    (90%)
    full (100%)
    Team Cohesion
    (TEAM)
    very difficult
    interactions
    some difficult
    interactions
    basically
    cooperative
    interactions
    largely
    cooperative
    highly
    cooperative
    seamless
    interactions
    Process Maturity
    (PMAT)
    Weighted average of “Yes” answers to CMM Maturity Questionnaire
    * % significant module interfaces specified, % significant risks eliminated

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  17. Cost Factors

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  18. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 18
    COCOMO II - Inputs

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  19. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 19
    Scale Drivers Rating
    Scale Factors (Wi
    ) Very Low Low Nominal High Very High Extra High
    Precedentedness
    (PREC)
    thoroughly
    unprecedented
    largely
    unprecedented
    somewhat
    unprecedented
    generally
    familiar
    largely
    familiar
    throughly
    familiar
    Development
    Flexibility (FLEX)
    rigorous occasional
    relaxation
    some
    relaxation
    general
    conformity
    some
    conformity
    general
    goals
    Architecture/Risk
    Resolution (RESL)*
    little (20%) some (40%) often (60%) generally
    (75%)
    mostly
    (90%)
    full (100%)
    Team Cohesion
    (TEAM)
    very difficult
    interactions
    some difficult
    interactions
    basically
    cooperative
    interactions
    largely
    cooperative
    highly
    cooperative
    seamless
    interactions
    Process Maturity
    (PMAT)
    Weighted average of “Yes” answers to CMM Maturity Questionnaire
    * % significant module interfaces specified, % significant risks eliminated

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  20. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 20
    COCOMO II - Inputs

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  21. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 21
    1. Product Factors
    1.1. Required Reliability (RELY)
    1. 2. Data Base Size (DATA)
    1. 3. Complexity (CPLX)
    1. 4. Developed for Reusability (RUSE)
    1. 5. Documentation (DOCU)

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  22. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 22
    2. Personnel factors
    2.1 Analyst capability (ACAP)
    2.2 Programmer (Software Engineer) capability (PCAP)
    2.3. Applications experience (APEX)
    2.4. Platform (or VM) experience (PLEX)
    2.5. Language and tool experience (LTEX)
    2.6. Personnel continuity (PCON)

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  23. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 23
    3. Platform Factors
    3.1. Time constraint (TIME)
    3.2. Storage constraint (STOR)
    3.3. Platform volatility (PVOL)

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  24. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 24
    4. Project Factors
    Project Factors
    4.1. Use of Software tools (TOOL)
    4.2. Multisite development (SITE)
    4.3. Required schedule - stretch-out or acceleration (SCED)
    Multisite development

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  25. Javier Gonzalez-Sanchez | CSE360 | Summer 2017 | 25
    Reference
    • http://sunset.usc.edu/research/COCOMOII/
    expert_cocomo/drivers.html
    • Chapter 23

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  26. CSE360 – Introduction to Software Engineering
    Javier G onzalez-Sanchez
    javiergs@ asu.edu
    Sum m er 2017
    Disclaim er. These slides can only be used as study m aterial for the class C SE360 at ASU. They cannot be distributed or used for another purpose.

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