1. Tutorial: Software Cost Estimation Tools – COCOMO II and COCOTS
Ye Yang
Center for Software Engineering
University of Southern California
2018/9/17

2. Part I: COCOMO II Model and Demo
2018/9/17

3. 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 is a combination of methods
compare and iterate estimates, reconcile differences
COCOMO is the most widely used, thoroughly documented and calibrated cost model
Price-to-win
Top-down
Bottom-up
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4. COCOMO Background COCOMO - the “COnstructive COst MOdel”
COCOMO II is the update to COCOMO 1981
ongoing research with new data collection and model 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 can be used as a framework for cost estimation and related activities
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5. COCOMO Black Box Model COCOMO II product size estimate
development, maintenance
cost and schedule estimates
product, process,
platform, and personnel
attributes
COCOMO II
reuse, maintenance,
and increment parameters
cost, schedule distribution by
phase, activity, increment
organizational
project data
recalibration to
organizational data
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6. COCOMO Submodels
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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7. COCOMO Effort Formulation
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8. 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 Model-Based Architecting and Software Engineering (MBASE) process
Effort and schedule are distributed among different phases and activities per work breakdown structure of chosen process
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9. MBASE Phase Distributions
see COCOMO II book for complete phase/activity distributions
Phase
Effort %
Schedule %
Inception 6
12.5
Elaboration 24
37.5
Construction 76
62.5
Transition 12
12.5
COCOMO Total
100
100
Project Total
118
125
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10. 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
2018/9/17

11. Scale Drivers Precedentedness (PREC) Development Flexibility (FLEX)
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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12. Scale Factors
Sum scale factors SFi across all of the factors to determine a scale exponent, B, using B = S SFi
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13. Cost Drivers Product Factors Platform Factors Personnel 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)
2018/9/17

14. 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?
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15. 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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16. 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.
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17. COCOMO Reuse Model
A nonlinear estimation model to convert adapted (reused or modified) software into equivalent size of new software:
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18. 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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19. 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 nonexecutable statements that affect an assembler's or compiler's interpretation of other program elements
Codecount tool available on USC web site
2018/9/17

20. USC COCOMO II Demo
2018/9/17

21. Part II: COCOTS Model and Demo
2018/9/17

22. 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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23. Relationship between CII and COCOTS
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24. COTS Assessment Sub-model
COTS Assessment: the activity of determining the appropriateness or feasibility of using specific COTS products to fulfill required system functions.
2018/9/17

25. 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.
2018/9/17

26. 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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27. COTS Glue Code Sub-model Formula
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28. 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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29. COCOTS Demo
2018/9/17

30. Contact Ye Yang Tel: 1 (213) 740-6470 Fax: 1 (213) 740-4927
2018/9/17