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UNDERSTANDING and

EFFECTIVELY USINGFUNCTIONAL MEASUREMENT

Presented ByThe David Consulting Group

www.davidconsultinggroup.com

NYC SPIN

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The Need for Sizing

Function Point Overview

Effective Use of Function Points

PRESENTATION HIGHLIGHTS

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CRITICAL SOFTWARE ISSUES CRITICAL SOFTWARE ISSUES

Understanding the Customer’s Requirements

Effectively Sizing the Requirements

Accurately Estimating the Deliverable

Managing a Successful Delivery

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CHARACTERISTICS OF AN EFFECTIVE SIZING METRICCHARACTERISTICS OF AN EFFECTIVE SIZING METRIC

Meaningful to developer and user

Defined (industry recognized)

Consistent (methodology)

Easy to learn and apply

Accurate, statistically based

Available when needed (early)

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Consistent method

Easy to learn

Available early in the lifecycle

Acceptable level of accuracy

Meaningful internally and externally

Results are normalized across different environments

Function Point Analysis is a standardized method for measuring the functionality delivered to an end user.

FUNCTION POINTS IS AN EFFECTIVE SIZING METRIC

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FUNCTION POINT ANALYSIS

Definition

Standard method for measuring software development from the customer’s point of view

Objectives

Measure software development and maintenance independently of technology used for implementation

Measure functionality that the user requests and receives

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FUNCTION POINT ANALYSIS - A LOGICAL VIEW

Physical

Lines of code or

programs/modules

Physical database or files

Physical transactions (screens)

Logical

Functionality required

Logical groups of user data

Business processes

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THE FUNCTION POINT METHODOLOGY

THE FUNCTION POINT METHODOLOGY

External Inputs

External Outputs

External Inquiries

Internal Logical Files

External Interface Files

External Input

External Inquiry

External Output

InternalLogical

Files

External Interface

File

Five key components are identified based on logical user view

Application

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LOGICAL VIEW OF USER REQUIREMENT

USER

LIST OF MOLDSWORK CENTERS

PARTS

PLANT MOLDS

PLANT INFORMATION CENTER

USER

BILL OF MATERIALS

PARTS LISTING

USER

ORDERPARTS

USER

CHANGEBILL

External Inquiries

Internal Logical Files

External Output

External Inputs

InterfaceVENDORSUPPLY

VENDOR INFORMATION

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Complexity

RecordElement

Types

Data Elements (# of unique data fields)

or File Types Referenced

Low Average High Low

Low Average

HighAverage High

Components: Low Avg. High Total

Internal Logical File (ILF) __ x 7 __ x 10 __ x 15 ___

External Interface File (EIF) __ x 5 __ x 7 __ x 10 ___

External Input (EI) __ x 3 __ x 4 __ x 6 ___

External Output (EO) __ x 4 __ x 5 __ x 7 ___

External Inquiry (EQ) __ x 3 __ x 4 __ x 6 ___

___Total Unadjusted FPs

Data Relationships

Each identified component is assigned a Function Point size value based upon the make-up and complexity of the data

1 3

3

THE FUNCTION POINT METHODOLOGY

THE FUNCTION POINT METHODOLOGY

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General System Characteristics

Data Communication On-Line Update

Distributed Data Processing Complex Processing

Performance Objectives Reusability

Heavily Used Configuration Conversion & Install Ease

Transaction Rate Operational Ease

On-Line Data Entry Multiple-Site Use

End-User Efficiency Facilitate Change

The final calculation is based upon the Unadjusted FP count X VAF

14 General Systems Characteristics are evaluated and used to compute a Value Adjustment Factor (VAF)

THE FUNCTION POINT METHODOLOGY

THE FUNCTION POINT METHODOLOGY

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SIZING THE REQUIREMENT

USER

ADD, CHG INVOICES

PAYMENTS

VENDOR

INVOICES

ACCOUNTS PAYABLE

USER

PAYMENTS

USER

PAYMENTSTATUS

USER

PAIDINVOICES

PURCHASEORDER INFO

PURCHASEORDERSYSTEM

External Interface FileExternal Inputs

External Input

External Inquiry

External Output

Internal Logical Files

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Components: Low Avg. High Total

Internal Logical File (ILF) X 7 2 X 10 1 X 15 35

External Interface File (EIF) X 5 X 7 1 X 10 10

External Input (EI) 1 X 3 X 4 2 X 6 15

External Output (EO) 1 X 4 X 5 X 7 4

External Inquiry (EQ) X 3 1 X 4 X 6 4 68

COMPONENTS ARE ASSESSED BASED UPON COMPLEXITY:

Data Element Types (Fields or Attributes)

File Types Referenced (ILFs or EIFs) Record Element Types (Data Sub-Groups)

Function Point Count

Complexity

DETERMINE THE FUNCTION POINT COUNT

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WHEN TO COUNT FUNCTION POINTS

CORRECTIVEMAINTENANCE

PROPOSAL DESIGN TESTING DELIVERY REQUIREMENTS

CONSTRUCTION

SIZING

Initial UserRequirements

Initial TechnicalRequirements

FinalFunctionalRequirements

FeasibilityStudy

SIZING SIZING

ChangeRequest

ScopeAdjustment

SIZING SIZING

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Purpose• To promote and encourage use of Function Points• To develop consistent and accurate counting guidelines

Benefits• Networking with other counters• IFPUG Counting Practices Manual• Research projects• Hotline• Newsletter• Certification

Utilization• Member companies include all industry sectors• Over 1200 members in more than 30 countries

INTERNATIONAL FUNCTION POINT USERS GROUP (IFPUG)

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EFFECTIVE USE OF FUNCTION POINTS

Requirements Management

Estimating

Benchmark Comparisons

Managing Change

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Functionality requested by the user may be organized into

logical parts that match the five function point components

MANAGING REQUIREMENTS

USER

ADD, CHG INVOICES

PAYMENTS

VENDOR

INVOICES

ACCOUNTS PAYABLE

USER

PAYMENTS

USER

PAYMENTSTATUS

USER

PAIDINVOICES

PURCHASEORDER INFO

PURCHASEORDERSYSTEM

External Interface FileExternal Inputs

External Input

External Inquiry

External Output

Internal Logical Files

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= 3200 square feet

How long will it take to build?

FUNCTION POINT SIZE –SO WHAT?

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DEFINITION CAPABILITY ESTIMATE

Sc

he

du

le

Effort Costs

PROJECTSIZE

X X RISKFACTORS

PROJECTCOMPLEXITYREQUIREMENT

ESTIMATING MODEL

FUNCTION POINTS

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RISK FACTORSRISK FACTORS

Estimates will also vary based upon a variety of

risk factors: Technology Applied such as tools, languages, reuse, platforms Process/Methodology including tasks performed, reviews,

testing, object oriented Customer/User and Developer skills, knowledge, experience Environment including locations, office space System Type such as information systems; control systems,

telecom, real-time, client server, scientific, knowledge-based, web

Industry such as automotive, banking, financial, insurance, retail, telecommunications

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Rate of DeliveryFunction Points per Person Month

0200

400600800

100012001400

1600

180020002200

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

SoftwareSize

ESTABLISHING A BASELINE

Performance Productivity

A representative selectionof projects is measured

Size isexpressedin terms of functionalitydelivered to theuser

Rate of delivery is a measure of productivity

Organizational Baseline

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COMPARISONS TO INDUSTRY

Industry Baseline Performance

Rate of DeliveryFunction Points per Person Month

0200

400600800

100012001400

1600180020002200

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

SoftwareSize

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PERFORMANCEPRODUCTIVITY

CAPABILITIES

PERFORMANCE

PROCESSIMPROVEMENT

TIME TO MARKET

RESOURCES

DEFECTS

BUSINESS VALUE

DELIVERABLES

SKILL LEVELS

PROCESS

TECHNOLOGYCOSTS

BARRIERS

MEASURED PROFILE

BASELINE PERFORMANCE

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CHANGE OF SCOPE MANAGEMENT

Initial InterimEstimate Estimate Estimate Variance

Function Points 500 650 +150

Effort (months) 33 43 +10

Schedule (months) 11 14 +3

Staffing Levels (FTE) 3 3 -0-

Production Rate (FP/mo) 15 15 -0-

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Change of Scope Inputs Outputs Inquiries Files Interfaces Total

Add vendor function 6 - 4 3 2 100

Graphical display - - 5 - - 20

Banking System 3 1 1 1 - 20

Mandatory Changes - 2 - - - 10

Total 150

COMMUNICATING CHANGES IN SCOPE

Function Point

Change of Scope Summary

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Additional Additional AdditionalFP Effort Cost Schedule

Change in Scope Count (staff mo.) ($000)___ (calend. mo.)

Add Vendor Function 100 7 100 2.0

Graphical Displays 20 1.2 20 .4

Banking System 20 1.2 20 .4

Mandatory Changes 10 .6 10 .2

Total 150 10 $150 3.0 mos.

COMMUNICATING IMPACT AND OPTIONS

OPTIONS

1. Increase funding level and schedule

2. Reduce functionality, or do not accept change

3. Trade off quality and maintenance costs for schedule

4. Delay delivery of change

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GENERAL INFORMATION

International Function Point Users Group

www.ifpug.org International Software Benchmarking Standards

Group www.isbsg.org.au

Measuring The Software Process: A Practical Guide To Functional Measurements, Prentice Hall, 1996

Function Point Analysis; Measurement Practices for Successful Software Projects, Addison-Wesley, 2001