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(c) 2004-2008 USC CSSE CSCI 577a 2008 COCOMO Tutorial 1
577a 2008 Tutorial:Software Cost Estimation Tools
– COCOMO II and COPSEMO and COCOTS
A Winsor Brown
Center for Systems and Software EngineeringUniversity of Southern California
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Prepare Your Machine• 1. Copy COCOMO II folder to the Desktop from
My Computer / LabApps / Programs / COCOMO_II OR If you enough rights, download and install from the CD e.g., D:\CII2000.EXE
• 2. Download COCOMO_II_2000.3 from Class Website CSSE.USC.edu >> Courses >> Current >> CSCI 577 (AKA http://greenbay.usc.edu/csci577/fall2008/site/tools) to the same folder on the desktop OR to the same folder you in which you installed COCOMO II
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CS577abc Course/Project Characteristics• Learn by Doing
• Real Projects for Real Clients
• Teaches Software Engineering of Large systems using small e-services/tools projects
• 577A: most projects through [preliminary LCA]
• 577B: ½ as many projects—Construction, Transition
• 577C [someday soon]: Maintenance and Enhancement
• Teaches Software Engineering of Medium/Large systems using small e-services or tools projects
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Part I: COCOMO II Model and Demo
If you haven’t done so already, Download COCOMO II.2000.3 from the class Tools Website; Quietly, in parallel with next few slides, Copy folder “COCOMO II” to the desktop; Start the Help: Click on Help.html; explore the Model Manual—find basic equation.Start COCOMO II.2000.3; Estimate a project with
2,000 lines of code
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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
• Best approach: a combination of at least two methods– compare and iterate estimates– reconcile differences
• COCOMO is the most widely used, thoroughly documented and calibrated cost model; and free
– Price-to-win– Top-down– Bottom-up– Parametric
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COCOMO Background
• COCOMO - the “COnstructive COst MOdel”– COCOMO II is the update to COCOMO 1981 – Results from ongoing research with new data collection & model calibration
(SFs; more data points; new ratings values; Bayesian calibration)
• Originally developed by Dr. Barry Boehm and published in 1981 book Software Engineering Economics
• COCOMO II described in new book Software Cost Estimation with COCOMO II
• COCOMO II can be used as a framework for cost estimation and related activities
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RUP/ICM Anchor Points Enable Concurrent Engineering
VCR: Valuation Commitment Review DCR: Development Commitment ReviewACR: Architecting Commitment Review OCR: Operations Commitment Review
V C R
I R R
A C R
L C O
D C R
L C A
C C D
I O C
O C R
P R R
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COCOMO Black Box Model
COCOMO II
product size estimate
product, process, platform, and personnel attributes
reuse, maintenance, and increment parameters
organizationalproject data
development, maintenance cost and schedule estimates
cost, schedule distribution by phase and activity (for Elaboration and Construction!)
local recalibration toorganizational data
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COCOMO Sub-models• Applications Composition involves rapid development or prototyping
efforts to resolve potential high-risk issues such as user interfaces, software/system interaction, performance, or technology maturity. It’s sized with application points (weighted screen elements, reports and 3GL modules).
• The Early Design model involves exploration of alternative software/system architectures and concepts of operation using function points and a course-grained set of 7 cost drivers.
• The Post-Architecture model involves the actual development and maintenance of a software product using source instructions and / or function points for sizing, with modifiers for reuse and software breakage; a set of 17 multiplicative cost drivers; and a set of 5 factors determining the project's scaling exponent.
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# of cost driversEffort (person-months) = A (Size)BΠ EMi
i=1• Where:
– A is a constant derived from historical project data (currently A = 2.94 in COCOMOII.2000)
– Size is in KSLOC (thousand source lines of code), or converted from function points or object points
– B is an exponent for the diseconomy of scale dependent on five additive scale drivers according to b = .91 + .01*ΣSFi,where SFi is a weighting factor for ith scale driver
– EMi is the effort multiplier for the ith cost driver. The geometric product results in an overall effort adjustment factor to the nominal effort.
• Automated translation effects are not included
COCOMO Effort Formulation
Quietly: Estimate a project with 2,000 lines of code using COCOMOII_2000.3
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1st Run of COCOMO II
• Start COCOMO II• Edit / Add Module Or Click on• Set Size: Click on
• Select “SLOC” Method
• Enter SLOC
• Save project in folder: “Single”
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1st Run of COCOMO II (cont.)
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Coverage of Different Processes• COCOMO II provides a framework for tailoring the model to
any desired process• Original COCOMO was predicated on the waterfall process
– single-pass, sequential progression of requirements, design, code, test
• Modern processes are concurrent, iterative, incremental, and cyclic– e.g. Rational Unified Process (RUP), the USC Lean ICM for
Software process • Effort and schedule are distributed among different phases
and activities per work breakdown structure of chosen process
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RUP/ICM Anchor Points Enable Concurrent EngineeringV C R
I R R
A C R
L C O
D C R
L C A
C C D
I O C
O C R
P R R
VCR: Validation Commitment Review DCR: Development Commitment ReviewACR: Architecting Commitment Review OCR: Operations Commitment Review
COCOMO II covers ONLY E&C (A/F & D[C])
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RUP & Lean ICM for Sw Phase Distributions
RUP Phases* Lean ICM for Software Phase
Effort % Schedule %
Inception Exploration 1 2.5
Inception Valuation 5 10Elaboration Foundations 24 37.5
Construction ICM Development: Code and Test
76 47.5
Transition ICM Development: [System] Integration
12 12.5
COCOMO Total 100 100Project Total 118 125
* see COCOMO II book for complete phase/activity distributions
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Part I: COCOMO II Model and Demo
• Quietly, in parallel with next few slides, copy folder with “Software Estimation” to the desktop; Download COCOMO II.2000.3 from the class Tools Website; Start the Help; Start COCOMO II.2000.3;
• Make estimate a realistic project with 2,000 lines of code: Add REVL!
• Save Project as 2ndRun
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2nd Run COCOMO II
• Set REVL to 15% (a good first guess)
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Cost Factors• Significant factors of development cost:
– scale drivers are sources of exponential effort variation– cost drivers are sources of linear effort variation
• product, platform, personnel and project attributes• effort multipliers associated with cost driver ratings
– Defined to be as objective as possible
• Each factor is rated between very low and very high per rating guidelines– relevant effort multipliers adjust the cost up or down
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Scale Drivers• Precedentedness (PREC)
– Degree to which system is new and past experience applies• Development Flexibility (FLEX)
– Need to conform with specified requirements• Architecture/Risk Resolution (RESL)
– Degree of design thoroughness and risk elimination• Team Cohesion (TEAM)
– Need to synchronize stakeholders and minimize conflict• Process Maturity (PMAT)
– SEI CMM process maturity rating
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Scale Factors• Sum scale factors SFi across all of the factors to determine
a scale exponent, B, using B = .91 + .01 Σ SFi
Scale Factors (Wi) Very Low Low Nominal High Very High Extra HighPrecedentedness
(PREC)thoroughlyunprecedented
largelyunprecedented
somewhatunprecedented
generallyfamiliar
largelyfamiliar
throughlyfamiliar
DevelopmentFlexibility (FLEX)
rigorous occasionalrelaxation
somerelaxation
generalconformity
someconformity
generalgoals
Architecture/RiskResolution (RESL)*
little (20%) some (40%) often (60%) generally(75%)
mostly(90%)
full (100%)
Team Cohesion(TEAM)
very difficultinteractions
some difficultinteractions
basicallycooperativeinteractions
largelycooperative
highlycooperative
seamlessinteractions
Process Maturity(PMAT)
Weighted average of “Yes” answers to CMM Maturity Questionnaire
* % significant module interfaces specified, % significant risks eliminated
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Cost Drivers• Product Factors
– Reliability (RELY)– Data (DATA)– Complexity (CPLX)– Reusability (RUSE)– Documentation (DOCU)
• Platform Factors– Time constraint (TIME)– Storage constraint (STOR)– Platform volatility (PVOL)
• Personnel factors– Analyst capability (ACAP)– Program capability (PCAP)– Applications experience (APEX)– Platform experience (PLEX)– Language and tool experience
(LTEX)– Personnel continuity (PCON)
• Project Factors– Software tools (TOOL)– Multisite development (SITE)– Required schedule (SCED)
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Example Cost Driver - Required Software Reliability (RELY)
• Measures the extent to which the software must perform its intended function over a period of time.
• Ask: what is the effect of a software failure?
Very Low
Low
Nominal
High
Very High
Extra High
RELY
slight inconvenience
low, easily recoverable losses
moderate, easily recoverable losses
high financial loss
risk to human life
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Significant CSCI577A Scale Factors• PREC• RESL
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Significant CSCI577A Effort MultipliersDATA DOCU PCON
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Significant CSCI577A Effort MultipliersDATA DOCU PCON
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Part I: COCOMO II Model and Demo Exercise 3
• Set Significant SF• Set Significant EAFs • Save Project as 3rdRun
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3rd Run COCOMO II
• Set PREC to Low
• Set RESL to High
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3rd Run COCOMO II (cont.)
• Set RELY to 50% of Low to Nominal
• Set DATA to Low
• Set DOCU to High
• Set PCON to Very Low
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3rd Run COCOMO II (cont.)
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Add Reused Component: Realistic Estimates
• Define some Re-Use Model• Do another exercise
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Reused and Modified Software
• 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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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.
Relativecost
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 LinearAssumption
Data on 2954NASA modules
[Selby,1988]
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COCOMO Reuse Model• A nonlinear estimation model to convert adapted
(reused or modified) software into equivalent size of new software:
AAF DM CM IM= + +0 4 0 3 0 3. ( ) . ( ) . ( )
ESLOCASLOC AA AAF SU UNFM
AAF=+ +
≤[ ( . ( )( ))]
, .1 0 02100
05
ESLOCASLOC AA AAF SU UNFM
AAF=+ +
>[ ( )( )]
, .100
05
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COCOMO Reuse Model (cont’d)• ASLOC - Adapted Source Lines of Code• ESLOC - Equivalent Source Lines of Code• AAF - Adaptation Adjustment Factor• DM - Percent Design Modified. The percentage of the adapted software's
design which is modified in order to adapt it to the new objectives and environment.
• CM - Percent Code Modified. The percentage of the adapted software's code which is modified in order to adapt it to the new objectives and environment.
• IM - Percent of Integration Required for Modified Software. The percentage of effort required to integrate the adapted software into an overall product and to test the resulting product as compared to the normal amount of integration and test effort for software of comparable size.
• AA - Assessment and Assimilation effort needed to determine whether a fully- reused software module is appropriate to the application, and to integrate its description into the overall product description. See table.
• SU - Software Understanding. Effort increment as a percentage. Only used when code is modified (zero when DM=0 and CM=0). See table.
• UNFM - Unfamiliarity. The programmer's relative unfamiliarity with the software which is applied multiplicatively to the software understanding effort increment (0-1).
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Sizing - Lines of Code• Source Lines of Code (SLOCs) = logical source statements
• Logical source statements = data declarations + executable statements
• Executable statements cause runtime actions
• Declaration statements are non-executable statements that affect an assembler's or compiler's interpretation of other program elements
• CodeCount tool available on CSSE website
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USC COCOMO II Exercise 4• Re-do COCOMO II Estimation
– Size: 3300 Total SLOC in two modules; • Re-Use 1,500 SLOC from Open Source Library
– DM, CM = 0; IM = 50%; – Unfm=.80
• 1,800 new SLOC– SFs as appropriate based on earlier discussion
PREC to Low RESL to High
– EAFs as appropriate based on earlier discussion RELY to 50% Low to Nom DATA to Low DOCU to High PCON to Very Low
• Save project (4thRun) in new folder “2Modules”
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4th Run COCOMO II
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4th Run COCOMO II (cont.)
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Schedule and Effort Over Full SDLC*
• COCOMO II Covers Elaboration and Construction
• COPSEMO to spread Effort and Schedule over ALL phases – COPSEMO uses COCOMO_Charts.xls as a helper
* Software Development Life Cycle (of a system Increment)
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RUP/ICM Anchor Points Enable Concurrent EngineeringV C R
I R R
A C R
L C O
D C R
L C A
C C D
I O C
O C R
P R R
VCR: Validation Commitment Review DCR: Development Commitment ReviewACR: Architecting Commitment Review OCR: Operations Commitment Review
COCOMO II covers ONLY E&C (A/F & D[C])
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RUP & [Instructional] ICM for Sw Phase Distributions
RUP Phases* Lean ICM for Software Phase
Effort % Schedule %
Inception Exploration 1 2.5
Inception Valuation 5 10Elaboration Foundations 24 37.5
Construction ICM Development: Code and Test
76 47.5
Transition ICM Development: [System] Integration
12 12.5
COCOMO Total 100 100Project Total 118 125
* see COCOMO II book for complete phase/activity distributions
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COPSEMO Distributes Effort & Schedule
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Physical COCOMO II PSE (CoPSEMo) Extension
Stage Distributions
(COPSEMO Extension)
COCOMO II.2000 COCOMO II cost drivers
% Distributions of Schedule and Effort
Schedule calculated; SCED removed; PM & M distributed per stage
Baseline Effort & Sched.
COCOMO.xls
Main.csv & Phase.csv
Workhours per month
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Do a COPSEMO Run on 4th Example
• Export … (CSV to folder with saved 4thRun example) [creates Phases.csv and Modules.csv]
• Install COPSEMO: Save COPSEMO.xls to folder with saved example from http://greenbay.usc.edu/csci577/tools/COPSEMO/COPSEMOv8.xls
• Copy COCOMO_charts.xls from COCOMO Installation folder to folder with saved example
• Run COCOMO_charts.xls; Import; save and close• Run COPSEMOv8.xls (may have to fix link)
[Edit/Links .. Change Source]
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Size Estimation• By analogy with Wide-Band Delphi before LCO
– Ask each team member what they think the size might be
• Apply personal experience, • Look at completed projects, • Guess (WAG), • SWAG based on “modules” known to date
– Collect and share in a meeting: discuss why/how different people made their estimate
– Repeat – When stable, Size = (H + 4 X Ave. + L)/6
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Size Estimation• By analogy with Wide-Band Delphi after LCO
– Measure Size of Prototype Code (CodeCount, or other tools)– Measure Size of Reused Code (CodeCount, or other tools)– Ask each team member what they think the final size might
be• Extrapolate from prototype (apply personal experience)• Guess (WAG), • SWAG based on “modules” known to date
– Collect and share in a meeting: discuss why/how different people made their estimate
– Repeat – When stable, Size = (H + 4 X Ave. + L)/6
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Size Estimation• By analogy with Wide-Band Delphi before LCA Draft
– Measure Size of “final” Prototype Code; provide along with original prototype code measure
– Measure Size of Reused Code (CodeCount, or other tools)– Ask each team member what they think the final size might
be• Extrapolate from prototypes (apply personal experience?)• Guess (WAG), • SWAG based on “modules” known to date
– Collect and share in a meeting: discuss why/how different people made their estimate
– Repeat – When stable, Size = (H + 4 X Ave. + L)/6
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COCOMO II Estimates in 577A
For Homework: “Homework 4: Cost Estimation”; Due 09/26/08!
For Project
• Before FCR/ACR/LCO (for ARB)
• After FCR/ACR/LCO ARB (for grading)
• Before DCR/LCA (for ARB)
• After DCR/LCA ARB (after re-scoping guidance) (for grading, “plan” for 577B, or actuals)
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Incremental Commitment Model in Software Engineering Class
06/24/08 ©USC-CSSE 49
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Part II: COCOTS Model and Demo
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Relationship between CII and COCOTS
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COCOTS
• COCOTS is the acronym for the Constructive COTS integration cost estimation model
• A member of the USC COCOMO II family of cost estimation models
• For estimating the expected initial cost of integrating COTS software into a new software system development
• Three sub-models: – COTS Assessment– COTS Tailoring– COTS Glue code development
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COTS Assessment Sub-model• COTS Assessment:
the activity of determining the appropriateness or feasibility of using specific COTS products to fulfill required system functions.
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COTS Tailoring Sub-model• COTS Tailoring: the activity associated with setting or
defining shell parameters or configuration options available for a COTS product, but which do not require modification of COTS source code, including defining I/O report formats, screens, etc.
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COTS Glue Code Sub-model
• COTS “glue” code/integration refers to software developed in-house and composed of – 1) code needed to facilitate data or information exchange
between the COTS and the system or other COTS;
– 2) code needed to connect the COTS into the system or other COTS but does not necessarily enable data exchange;
– 3) code needed to provide required functionality missing in the COTS AND which depends upon or must interact with the COTS.
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COTS Glue Code Sub-model Formula
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Total COCOTS Estimation
• Sum of three sub-models’ estimates:– EffortCOT = EffortA + EffortT + EffortGC
• “Grand” total effort for developing a COTS-Based System (CBS):– EffortCBS = EffortCOC + EffortCOT
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Questions and Answers• Questions from you?
• Question from HHGG: “the great question of Life, The Universe and Everything”.
• Answer: 42! (1010102 )