cocomoii_investigation

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BeyondTest

Literature ReviewCOCOMO II Investigation

Version 0.1


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Literature Review Version: 0.1COCOMO II Investigation Date: 29/April/2005COCOMO_investigation.doc

Revision HistoryDate Version Description Author

29/April/2005 0.1 This is just first literature review about

COCOMO II. The main resource is thebook, cf. reference section.

Hawk Wang ( )

Public BeyondTest 2005 Page 2
http://beyondtest.objectis.net/hawkwang/mehttp://beyondtest.objectis.net/hawkwang/mehttp://beyondtest.objectis.net/hawkwang/mehttp://beyondtest.objectis.net/hawkwang/me


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Table of Contents1. Introduction 4

2. COCOMO II models 4 2.1 General methodology 5 2.2 Concrete Models - Early Design Model & Post-Architecture Model 6

2.2.1 Model Formula 6 2.2.2 Scale Factors 7 2.2.3 Effort Multipliers 7

2.3 Model Calibration and Customization 9 2.4 Model Application 10

3. Good Points for Research Project 11

4. Summery 11

5. Reference 11



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1. IntroductionThe COCOMO cost estimation model is used by thousands of software project managers, and is based on a

study of hundreds of software projects. Unlike other cost estimation models, COCOMO is an open model, so all of the details are published, including:

The underlying cost estimation equations

Every assumption made in the model

Every definition

The costs included in an estimate are explicitly stated

Because COCOMO is well defined, and because it doesn't rely upon proprietary estimation algorithms, ithas following advantages:

COCOMO estimates are more objective and repeatable than estimates made by methods relying on proprietarymodels

COCOMO can be calibrated to reflect your software development environment, and to produce more accurateestimates

Now, COCOMO II is the current version of COCOMO model. It is enhanced based on COCOMO 81model to accommodate different approaches to software development, for example, incremental development.

COCOMO II incorporates a range of sub-models that produce increasingly detailed software estimates:

Application composition model . Used in the earliest phases or spiral cycles, which will generally involveprototyping using application composition capability.

Early design model . Used in next phases or spiral cycles, which will generally involve exploring architecturalalternatives or incremental development strategies.

Post-architecture model . Once the project is ready to develop and sustain a fielded system, it should have a life-cycle architecture, which provides more accurate information on cost driver inputs and enables more accurate costestimates. Post-architecture model is suitable for such phases.

Generally speaking, COCOMO II can be used for:

Software development approach

Budget decisions

Production tradeoffs

IT capital planning

Investment options

Management decisions

Prioritizing projects

SPI strategy

Since COCOMO model has a lot of aforementioned advantages, how its approach can be used for our currentresearch work is worth investigating.

2. COCOMO II modelsAccording the applicability, three COCOMO II models are introduced. Following figure gives an



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illustration about model applicability. In this documentation, only Early Design Model and Post-Architecture Modelare discussed to simplify the contents.

Figure 1 Model Applicability

2.1 General methodologyThe essence of COCOMO II model is non-linear regression modeling. Figure 2 is used to depict such

approach.

CostCOCOMO IISize (Parameters)

Schedule

Factors

(Software Platform, Product,

Personnel & Project attributes)

Figure 2 COCOMO II model illustrations

Here, size can be estimated as KLOC or Function Points. In order to estimate system size, four importantfactors should be considered.



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2.2.2 Scale Factors

RESL

TEAMFLEX

Figure 4 Scale Factors

Table 1 gives the detailed descriptions for each scale factors. Following factors are not only suitable for Post-Architecture Model, but also suitable for Early Design Model.

Table 1 Scale Factors Glossary

Abbreviation Full Term DescriptionPREC Precedentedness It is used to describe the similarity to previously

developed projects. If a product is similar to severalpreviously developed projects, then the precedentedness ishigh.

FLEX Development Flexibility It is used to describe the uncontrollability of project.RESL Architecture/Risk Resolution As full termTEAM Team Cohesion Accounts for the sources of project turbulence and

entropy.PMAT Process Maturity Used to capture organization level development process

maturity.

2.2.3 Effort Multipliers

The later in project development, the more information can be retrieved for effort and schedule estimation. So, 17effort multipliers for Post-Architecture Model are introduced, while only 6 ones for Early Design Model.

Figure 5 and 6 are used to describe effort multipliers for Post-Architecture Model and Early Design Model. We canregard the Early Design Model as a simplification of Post-Architecture Model.

PMATPREC

Scale Factors



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RELY ACAP

DATA PCAP TOOLTIME

PCONCPLXSITESTOR

Figure 5 Effort Multipliers for Post-Architecture Model

Figure 6 Effort Multipliers for Early Design Model

Table 2 gives the detailed descriptions for each effort multipliers. We add column scope to indicate the modelrelated.

Effort Multipliers

Product Factors

Platform Factors Personnel Factors

DOCU

RUSE

PVOL

APEX

SCEDPLEX

LTEX

Project Factors

Effort Multipliers

Product Factors

Platform Factors Personnel Factors

RCPX RUSE PDIFPERS PREX

SCED

Project Factors

FCIL



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Table 2 Effort Multipliers Glossary

Abbreviation Full Term Scope DescriptionRELY Required Software

ReliabilityPost-Architecture Model As full term

DATA Database Size Post-Architecture Model As full termCPLX Product

ComplexityPost-Architecture Model As full term

DOCU Documentationmatch to life-cycleneeds

Post-Architecture Model As full term

RUSE Developed forReusability

Post-Architecture ModelEarly Design Model

As full term

TIME Execution TimeConstraint


STOR Main StorageConstraint


PVOL Platform volatility Post-Architecture Model As full termACAP Analyst Capability Post-Architecture Model As full termPCAP Programmer

CapabilityPost-Architecture Model As full term

PCON PersonnelContinuity


APEX ApplicationsExperience


LTEX Language & ToolExperience


PLEX PlatformExperience


TOOL Use of SW tools Post-Architecture Model As full termSITE Multi-site

developmentPost-Architecture Model As full term

SCED Required Dev.Schedule

Post-Architecture ModelEarly Design Model

As full term

RCPX Product Reliabilityand Complexity

Early Design Model Used to synthesize RELY, DATA,CPLX, and DOCU conditions.

PDIF Platform Difficulty Early Design Model Used to synthesize TIME, STOR,and PVOL conditions.

PERS PersonnelCapability

Early Design Model Used to synthesize ACAP, PCAP,and PCON conditions.

PREX PersonnelExperience

Early Design Model Used to synthesize APEX, PLEX,and LTEX conditions.

FCIL Facilities Early Design Model Used to synthesize TOOL, and SITEconditions.

2.3 Model Calibration and Customization

Current model parameters are estimated using 161 projects data. If COCOMO II model is selected by aconcrete organization, model calibration and customization should be considered.



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Process improvement decisions

The calibration procedure is the regression procedure. The data from the concrete organization are used toestimate the parameter A, B, C and D.

In some situation, organization may focus more on some cost drivers or factors that are not included in theCOCOMO II model, for example, security constraints. Then we can add one factor as SCON - security

constraints to the current model. A suitable rating scale for such factor should be developed and then themodel parameters can be calibrated again according to the real project data.

2.4 Model Application

The following figure gives an illustration about how to use COCOMO II model.

Re-scope

Figure 7 COCOMO II Application Illustrations

By using COCOMO II model, lots of analysis can be made:

Making investment decisions and business-case analysis

Setting project budgets and schedules

Performing tradeoff analysis Cost risk management

Development vs. reuse decisions

Legacy software phase-out decisions

Software reuse and product line decisions

System Objectives:

Functionality,

performance, qualityCOCOMO II

Project Parameters:

Personnel, Team,

Sites, Platform

Corporate Parameters:

Tools, Processes,

Reuse

Evaluate Corporate

SW Improvement

Stratigies

OK?

Execute

project to next

milestone Revise

milestones,

plans, resources

Accumulate

COCOMO II

calibration data

Recalibrate or

extendOCOMO II

OK?

Done?

No

Yes

Cost,

Schedules,

Risks

Cost, Schedules,

Quality drivers

Milestone plans,resources Milestone

Result

No

Revised

expectations

Milestone

Expectations

Yes

Improved

Corporate

parameters

No

Yes

End



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3. Good Points for Research Project

lowing good points are raised and may be used for our current

on

stimation

4. Summeryntation, we introduced the COCOMO II model, including modeling methodology, formula,its usage. Furthermore, some good points from investigation are raised for our current research

5. Referencery W. Boehm, etc., Software Cost Estimation with COCOMO II, Prentice Hall, 2000

Weakness: no cause analysis

During investigation of COCOMO II models, folresearch projects.

Factor Selecti

Value Rating & E

Model Predictability

Model Customization

Model Application

In this documeconcrete models andproject.

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