“Why Size Matters”

1QSM Associates, Inc.

Michael C. MahManaging Partner

QSM Associates, Inc.75 South Church Street

Pittsfield, MA 01201413-499-0988

Fax 413-447-7322e-mail:

michael.mah@qsma.com

“Why Size Matters”

Web Site: www.qsma.com

NYCity SPIN PresentiationNew York NY, May 2003

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“If you underestimate the size

of your next project, common

sense says that it doesn’t

matter which methodology you

use, what tools you buy, or

even what programmers you

assign to the job.”

Ed Yourdon on “Sizing”..

6QSM Associates, Inc.

Rifkin’s* Criteria:Estimation Processes

1) Commitments have to be based on work [scope] to be performed; therefore, there must be agreement on this

2) Estimates have to be based on a) the work to be performed and b) historical records of performance

3) Commitments must not exceed the capability to perform, or else there is no reason to estimate

* Stan Rifkin, Master Systems Inc.(formerly with Carnegie Mellon SEI)

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Sizing Has a Purpose

Productivity Measurement (Historical View)

Project Estimation (Future View)

Project Risk Tracking (Present View)

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Software Measurement and Management – 3

Key Areas

ProjectEstimation

“In-Flight”Tracking

Support FutureCommitments

ManageCommitmentCommitment

Analyze Performance on Commitment

ProjectHistory

Assess Viable Strategies

Monitor Status & ReplanPost Project Analysis

Make Commitment

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QSM Productivity Index (PI)(industry values by application type)

0 2 4 6 8 10 12 14 16 18 20 22 24

Productivity Index (PI) w/ ±1 Standard Deviation

Avionics

Business

Command and Control

Microcode

Process Control

Real Time

Scientific

System

Telecommunications

Information

Engineering

Real Time

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Example – Historical and New Project Assessment

Main Build Time vs. Size

1 10 100 1000

Months

1

10

100

SmartMed History QSM Industry Avg 1 Sigma Range

New + Modified Size

Project A history20 months

Project B history8.5 months

SmartMedDeadline – 6 months

SmartMed Schedule Target InconsistentWith History Trend

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Early Warning - Tracking Size for “In-Flight”

ProjectsSize

0

10

20

30

40

50

60

70

S 1 2 3 4 5 6 7 8S 1 2 3

ES

LOC

(thousands)

Oct'92

Jan'93

Apr Jul Oct Jan'94

Apr Jul Oct Jan'95

Apr Jul

Actual

Interpolated

Plan

Green CB

Yellow CB

S = Start

1 = HLD

2 = LLD

3 = UIT

4 = SIT

5 = SVT

6 = BT

7 = GA

8 = 99R

Size (ESLOC(K))PI 10.8 9.1 -1.7MBI 1.2 0.6 -0.6

Date 1/2/94 (14.1 mos)

Plan Actual Diff37.12 32.30 -4.82

Data are Consistentlyin the Amber Region

Example

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Cutter Consortium Study on Software Estimation

Source: Cutter Consortium, Benchmark Review Vol. 2, No. 8

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Perceptions of Size

Microsoft

Industry Leader?

Microsoft

Brutal Monopolist?

Different views aren’t necessarily crazy

None of us has sole possession of the truth

Not always Right/Wrong, more often a case of Right/Right

Function Points are a Savior

Function Points areEvil

Counting Code is Relevant

Counting Code is Stupid

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Ed Yourdon on “Sizing”..

“Studies by the Carnegie Mellon

SEI indicate that the most

common failing of

Level 1 (Ad-hoc) software

organizations is an inability to

make size estimates accurately.”

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The Common Obstacle to Software Sizing

“Never been asked to

consider size up front or

after the fact; always

equated size to effort i.e.

number of hours”

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Software Sizing

How do we Describethe Volume of Software?

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Many Functional Metrics Can be Used to Represent S/W Size

Subsystems

Entities

Function points

Modules

Objects

Programs

SLOC

Actions/Instructions/Statements

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Functional Metrics(Proxies)

They all represent what has to be created, but at different levels of abstraction

They all can be useful Knowing the scaling relationships, enables

us to use them effectively

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Size – Scaling Relationships

Objects 150 – 250 loc/Object Function Points 30 - 400 Modules 100 - 500 Programs 200 - 1400 Subsystems 4,000 - 12,000

Can Be Determined from Data

Typical Examples

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For Additional Information

Contact:

Michael MahManaging PartnerQSM Associates Inc.Clocktower Building75 So. Church St., Suite 600Pittsfield, MA 01201

Email: michael.mah@qsma.comWeb url: www.qsma.com