cse 7315 - sw project management / module 20 - more effort estimation models copyright © 1995-2006,...

CSE 7315 - SW Project Management / Module 20 - More Effort Estimation ModelsCopyright © 1995-2006, Dennis J. Frailey, All Rights Reserved

Slide 1

CSE7315M20

August 12, 2006

SMU CSE 7315Planning and Managing a

Software Project

Module 20More Effort Estimation Models

Slide # 2August 12, 2006

CSE 7315 - SW Project Management / Module 20 - More Effort Estimation ModelsCopyright © 1995-2006, Dennis J. Frailey,

All Rights ReservedCSE7315M20

Objectives of This Module

• To discuss some additional Effort Estimating models

• To discuss conversion from effort to cost

• To discuss more about Cocomo II




The Big Picturefor Cost Estimating

EstimateSize

EstimateEffort and

Cost

EstimateSchedule

Evaluate

Source InformationStatement of Work

RequirementsConstraintsStandardsProcesses

Historyetc.

WBS Size

Effort &

Cost

Schedule

OKCompleteDetailedPlanning

Revise &Negotiate

Not OK




Bottom-Up Effort Estimating




Architecture of Spreadsheet

Model BasedEffort Estimate

Other EffortEstimates ...

HistoricalSize Estimate

SoftwareReuse

Analysis

Final EffortEstimate

ProductivityBased Effort

Estimate

Other SizeEstimates ...

Final SizeEstimate

DelphiSize Estimate

Size / Reuse Effort Effort & Cost Schedules

Generic Schedule

Effort Schedule

Labor Schedule

Cost Schedule

0

5

10

15

20

25

M1 M2 M3 M4 M5 M6

Total

Build 1

Build 2




Bottom-Up Effort Estimating

• This method may take a lot of time

• It may or may not be based on size estimates




Bottom-Up Estimating Process

1) Break the software down into components -- as detailed as you can– Break down until the individual parts are

small enough for an individual to develop in a short time (1 week to 1 month perhaps)

– If you do not know, make a reasonable estimate of how you might break each part of the software into smaller parts

2) Estimate each part3) Combine estimates




Sample Breakdown

Database I/F

ErrorProcessor

Sort Module

Synchro-nizer

CommandProcessor

TableInterface

Joe Mary &

Jim

Bert &

Sally

Joe Bert Sally

ParserCode

GeneratorFile

SystemRun TimeSystem

UserInterface

ManageSoftware

Development

Build “C”Compiler

Build TestSuite

WriteDocumentation

WriteInstallationSoftware

Software for“C” Compiler




Sample Estimate

6 SW6 SW 1 SW1 SW4 SW4 SW 5 SW5 SW3 SW3 SW 4 SW4 SW

Joe Mary &

Jim

Bert &

Sally

Joe Bert Sally

12 SW 28 SW23 SW 14 SW18 SW

18 SW95 SW 33 SW 12 SW 22 SW

180 SW




For an Object Oriented DesignYou May Break it Up

Differently

Class“Query”

Subclass“User

Response”

Class“ErrorCode”

Class“Response”

Subclass“System

Response”

Subclass“Maintenance

Response”




Bottom-Up EstimatingBenefits

• Each part of the project is estimated by someone who knows that part well

• Individuals “buy in” to the estimate because it was based on their expertise

• It is easy to compare actuals with estimates and determine if and where you went wrong




Architecture of Spreadsheet

Model BasedEffort Estimate

Other EffortEstimates ...

HistoricalSize Estimate

SoftwareReuse

Analysis

Final EffortEstimate

ProductivityBased Effort

Estimate

Other SizeEstimates ...

Final SizeEstimate

DelphiSize Estimate

Size / Reuse Effort Effort & Cost Schedules

Generic Schedule

Effort Schedule

Labor Schedule

Cost Schedule

0

5

10

15

20

25

M1 M2 M3 M4 M5 M6

Total

Build 1

Build 2




Compare Results and Judge

Method Productivity Cocomo Bottom Up

J udged

Eff ort 376 402 358 360

Productivity 1.1 .9 1.2 1.2

Schedule 12.8 14.2 12 12




Cost Estimating




There are Many CostsOther Than Software

Development

WBS

EstimateSize and

ThenEffort

Estimate Costs Directlyor as % of

Development Costs

Software Developme

nt Tasks• requirement

s• design• code• ...

Other Tasks and Costs

• management

• travel• training• overhead• facilities• equipment• software• …

Convertto$

TotalCost

Estimate

TotalCost

Estimate




Turning Effort into Cost• Turning effort estimates into cost

estimates depends on many factors that depend on your specific company– Overhead rates– Cost of borrowing money– Methods of calculating profit margin– Allocations of management and support

expenses– Costs of capital equipment– etc.




One Way to Convert Effort to $

Category % of Total Salary Rate#

Requirements 10% $65/hourDesign 10% $50/hourCode 30% $40/hourTest 30% $30/hourOther 5% $15/houretc. etc.

# use rate per hour if effort is measured in staff-hours use rate per day if effort is measured in staff-days etc.




Multiply the Effort by the Percentages to get the Labor

Distribution and $10,000 hours:

1000 hours - requirements x $65 = $65,000

1000 hours - design x $50 = $50,000

3000 hours - code x $40 = $120,000

3000 hours - test x $30 = $90,000

etc.

Total: $xxx,xxx




A Note About theLabor Rate Chart

• Be sure to correlate the percentages with the “experience level” factors assumed in your effort estimate

>> It is tempting to cut costs estimates by boosting the percentage of lower cost staff -- check what this does to the cost drivers first!!! <<




Supplement - Cocomo II (1)

• Barry Boehm and his colleagues at the University of Southern California are working on a new version of Cocomo that better represents modern programming practices and such

• An initial version of the model has been released

• The next few slides will review some of the important concepts in the new model

(1) Boehm, et. al., USC Center for Software Engineering




Cocomo Versions and Limitations

Original (1981) - custom, “build to specs” software development projects

Ada (1989) - custom, written in Ada These models were not calibrated to:• Business software• Object-oriented software• Commercial, off-the-shelf application

composition• Evolutionary development




Cocomo II Objectives

• Fit lifecycle practices of the 21st century

• Support continuous improvement of the model

• Support evaluating the effects of software technology improvements on life cycle costs and schedules




Future Software PracticesMarketplace Model (1)

(1) extrapolated from Silvestri and Likasieicz, “Occupational Employment Projections,” [Bureau of Labor Statistics moderate-growth labor distribution scenario for the year 2005] Monthly Labor Review 114 (11), November 1991, pp. 64-94.

Infrastructure (operating systems, networks,major products) (0.75 Million

Performers in the U.S.)

End-User Programming

(55 Million Performers in the U.S.)

SystemIntegration(0.7 Million)

Application Composition (0.7 Million)

Application Generators &

Composition Aids (0.6 Million)




Duration of TypicalSW Development Effort

Infrastructure (operating systems,networks, major products)

1-6 years

SystemIntegration

Application Composition

1-6 months

Application Generators & Composition Aids

End-User Programming

1-6 hours




The Middle Layers

• Application Generators -- creation of prepackaged capabilities for end users


Application Generators and Composition Aids

(0.6 Million)





The Middle Layers (continued)



(0.6 Million)


• Application Composition -- from interoperable components such as GUI builders, database systems, object managers (middleware)




The Middle Layers (continued)

• System Integration -- similar to custom

applications but with heavy use of prepackaged tools

and application composition



(0.6 Million)





Cocomo II Strategy• Several submodels for the various sectors described

above• Tailoring of submodels to project details• Combination of submodels for each situation, as

required




Additional Cocomo II Information

Under development at University of Southern California, Cocomo II project.

For More Information on Cocomo II:HTTP://SUNSET.USC.EDU/

research/COCOMOII/index.html




Matching Models to SectorsEnd User Programming

– No Need for a Cocomo Model– Relatively short development

Application Composition– Based on Object Points (1)

Application Generator & System Integration– Tailored mix of Application Composition (for prototyping) and

more detailed models

(1) Banker, Kauffman, Kumar, “An Empirical Test of Object-Based Output Measurement Metrics in a Computer Aided Software Engineering Environment,” Journal of Management Information Systems, 1994.




Three-Stage Series of Models

1) (prototyping / application composition)Application composition model based on object points

2) (exploration of alternatives, incremental development)Early Design model based on function points and five cost drivers (one for each major category in original Cocomo)




Three-Stage Series of Models (continued)

3) (final development of fielded system)Post-Architecture model, similar to current Cocomo model. Uses SLOC or function points.




Each Stage ProducesThree Values

• Optimistic Estimate• Expected Value• Pessimistic Estimate

These correspond to the two outer curves and the “dots” shown on the next slide




Estimating Accuracy vs. Phase

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Feasibility Plans Design Detailed

Design

Code and

Test

Release

Upper Limit

Actual

Lower Limit

• Typical Estimate

• • • • •

•

•

•

Application Composition

Model Early Design Model

Post Architecture

Model




Module Summary• Bottom-up estimating can be costly and

slow, but generates strong “buy-in”• Cocomo II is an emerging approach that

applies Cocomo and other models to newer methods of software development

• Cocomo II also recognizes that estimates must be refined and updated as a project progresses




General References on Estimating Cost

Boehm, Software Engineering Economics (Prentice-Hall, 1981); Software Cost Estimation With COCOMO II (Prentice Hall, July 2000)

Boehm, et. al., Cost Models for Future Software Life Cycle Processes: Cocomo 2.0, Technical Report, USC Center for Software Engineering, Draft 2.0, September 6, 1994.

Brooks, Fred, The Mythical Man-Month, 1975 / 1995.

Tausworthe, R.C. Software Specifications Document, DSN Software Cost Model, Jet Propulsion Laboratory, JPL Publication 81-7 (1981).




END OFMODULE 20

cse 7315 - sw project management / module 20 - more effort estimation models copyright © 1995-2006,...

Documents