FAST Function Points

David SeaverDirector Estimation and Measurement

Fidelity Investmentsdavid.seaver@fmr.com

8-563-6753

Outline of the Presentation

• Overview of function points (IFPUG based Technique)• FAST Function Points Overview• An example of a requirements based Function Point Count• An example of a Screen based completed project Function Point

Count

What is a Function Point

• Function Points measure software size by quantifying thefunctionality provided to the user based solely on logical designand functional specifications. With this in mind, the objectives ofFP counting are to:– measure functionality that the user requests and receives– measure software development and maintenance rates and

size independently of the technology used forimplementation

– provide a normalizing measure across projects andorganizations

What is Function Point?

• Functionality as viewed from the user’s perspective

External Interface FilesExternal Input

External Output

External Inquiry

Application Being Considered

Other Applications

External Output

External Input

External Inquiry

InternalLogical

File

How to Count Function Points

How to Count Function Points

Displays

Reports

Master Files Size

ReferenceFiles

Signals

Control Files

Steps in FP Counting

• Determine Type of Count• Identify Counting Scope and Application Boundary• Count Data Functions• Count Transactional Functions• Determine Unadjusted Function Point Count• Determine Value Adjustment Factor• Calculate Adjusted Function Point Count

FP Overview: What Is Counted

EI

ILF

EIF

EQ

Key

Details

P1Update Master File

Master

File

P3

Master File

Details

WeeklySummaryReport

P2

Produce Weekly Report

Reference

File

anotherSystem

on

SystemBoundary

EO

Data Storage

• Internal Logical File (ILF)Logical group of data maintained by theapplication (e.g., Employee file)

• External Interface File (EIF)Logical group of data referenced but notmaintained (e.g., Global state table)

Transactions

• External Input (EI)Maintains ILF or passes control data intothe application

• External Output (EO)Formatted data sent out of application withadded value (e.g., calculated totals)

• External Query (EQ)Formatted data sent out of applicationwithout added value

Functional Size(Unadjusted Function Size)

Function Type Low Average High

EI x 3 x 4 x 6

EO x 4 x 5 x 7

EQ x 3 x 4 x 6

ILF x 7 x 10 x 15

EIF x 5 x 7 x 10

Value Adjustment Factor

• Based on 14 General System Characteristics (UserBusiness Constraints Independent of Technology)– Examples: data communications, response

times, end user efficiency, multiple sites andflexibility

• Adjusts FP count by up to + / - 35%

Software DevelopmentChallenges

• Size of Requirements

• Changes to Requirements

• Estimation Based on Requirements

• Measuring and Improving Productivity andQuality

Size of Requirements

• Requirements

– Complete

– Business Terms

– Mutual Understanding

– Document Assumptions

– Size

Changes to Requirements

• Changes to Requirements

– Change Inevitable

– Trade-offs

– Customer Definition of Quality

– Size

Estimation Based onRequirements

• Estimation Based on Requirements– Multiple Models– Weighted Inputs:

• Language• Skills• Methodology• Risk Factors• Size

– Historical Base

Function Points Some Resources

• International Function Point Users Group– http://www.ifpug.org/

• International

Problems (real and alleged) withFunction Points

• Takes a long time– experienced counter can count 1500 function points a day

• Boring• Cannot perform accurate count until design in reasonably

complete• Inconsistency

Function Points(My personal opinions)

• Core strength of the technique is the relationship it establishesbetween user transaction & data and software costs &schedules

• Very strong communication tool• Proactively applied early in a project function points can

accelerate the requirements and high level design process

Steps in FP Counting

IFPUG FASTDetermine Type of Count Document Purpose of EstimateIdentify Counting Scope and Application Boundary

Identify Scope and Boundary

Count Data Functions Count Transactions

Count Transactional Functions Assign Data Functions to appropriate transactions

Determine Unadjusted Function Point Count

Determine Unadjusted Function Point Count

Determine Value Adjustment Factor Determine Value Adjustment Factor

Calculate Adjusted Function Point Count

Calculate Adjusted Function Point Count

How to Accelerate FP Counts• Develop a profile of your Transactions and Data Functions• Example

– Most of my use case have following attributes• Create/new data function• Edit• No delete• Edit or delete has an implicit inquiry• Maintain 1 logical data group• 1 report

– In function point speak• 2 inputs add/edit• 1 inquiry• 1 file• 1 ouput

How to Accelerate FP Counts• Develop a profile of your typical complexity

– outputs are medium 5 Function Points– inputs are low 3 Function Points– inquiries are low 3 Function Points– files are low 7 Function Points– external interface files are not found 0 Function Points

• For my typical Use Case– 2 inputs 6 Function Points– 1 inquiry 3 Function Points– 1 output 5 Function Points– 1 File 7 Function Points

• General System Characteristics =1.12• AFP =23.52 round up to 24 Function Points for each use case

Accelerate Function Point Counts

• Take advantage of available Data• ISBGS has average complexity numbers for the projects in the

data base (700)• Also have product delivery rate data for industry and platform

– PDR = hour/function point– Platform

• Mainframe• Midrange• PC

• Useful as a inexpensive benchmarking tool

Low Average High ISBGSinputs 3 4 6 4.3outputs 4 5 7 5.4queries 3 4 6 3.8files 7 10 15 7.4xfiles 5 7 10 5.5

Accelerate Function Point Counts

• Low, Average and Highare the IFPUG valuesfor Transactions andData Functions

• Values in ISBGS columnare the average valuesfor the Transaction andData Functions from theInternational SoftwareBenchmarking GroupsDatabase of projects

Estimating Examples• Management wants to

know how cost went from$100K to $1.5M

• You can use functionpoints to explain whathappened

• You can use functionpoints to get approval ofwhat's happening beforeyou get into trouble

Cost Categories BSV PPI SRAFunction Points 93 819 1,436total hours 947 8,859 15,788Total Cost 99,481$ 885,876$ 1,578,803$ rate/hour 105 105 105person months 6 57 102person years 0.5 4.8 8.5Defects 13 147 273FP/PM 15 14 14Project Start 6/1/00 6/1/00 6/1/00SRA/PPI Complete 6/10/00 7/25/00 8/8/00TSD Complete 8/1/00 11/21/00 1/4/01TPD Complete 9/7/00 2/14/01 4/21/01SIT Complete 9/7/00 2/14/01 4/21/01System Test Complete 9/21/00 3/24/01 6/7/01Install Complete 9/27/00 4/8/01 6/25/01

Function Point Count at BSV

• Simple project, administer 35 data elements for all employees in thecompany, simple GUI, online help, maintain user access for securityreasons

• Total of 93 Function Points• Created from system context diagram

BSV Estimate 8 2 4 3 0 93 83 34 11 15 22 0

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maintain core personnel data 3 2 1 1

35 data elements, add,edit,delete 13 11 4 7 0

online help 2 2 1 9 0 8 7 0maintain users access data 3 1 1 13 0 4 7 0

Assumption Made to GenerateEstimate

• System developed in Oracle• Team has completed several Oracle Projects• Team has completed several projects of this type• Team has experience in this industry• Requirements are stable

Estimate At BSVBSV Estimate

Function Points

Function Points/Hours

Defects/Function Points

93 1.97 0.14

ActivitySystem Designers/Analysts

Programmers Test Engrs.

Project Mgt.

QA/CM

TechPubs

Total HoursActivity Length (Days)

Start Dates

End Dates

Requirements Analysis

104 0 49 12 17 7 189 9 6/1/2000 6/10/2000

Preliminary Design

76 24 30 10 12 6 157 28 6/2/2000 6/30/2000

Detail Design 115 36 45 15 18 9 236 54 6/7/2000 8/1/2000

Code and Unit Test

8 45 11 3 12 2 80 58 6/21/2000 8/18/2000

Integration and Test 35 24 59 7 39 7 171 72 6/27/2000 9/7/2000

System Integn & Test 20 7 20 3 16 3 68 112 6/1/2000 9/21/2000

Installation 17 6 9 2 11 2 47 62 7/27/2000 9/27/2000

Total 374 141 223 51 124 35 947 118 6/1/2000 9/27/2000

Function Point Count at SRASRA Size Estimate 74 13 24 34 0 819 731 318 70 91 252 0

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maintain core personnel data 3 2 1 135 data elements, add,edit,delete 13 11 4 7 0

online help 2 2 1 9 0 8 7 0maintain users access data 3 1 1 13 0 4 7 0

0 0 0 0 0

add 4 other data types 12 4 4 4support 5 different data feed formats 52 22 15 30 0

international data differences 2 1 1 UK 9 0 4 7 04 1 1 Japan 17 0 4 7 0

10 1 5 Germany 43 0 4 37 02 1 1 China 9 0 4 7 0

0 0 0 0 0Data Providers 7 7 7 data providers 0 38 0 52 0

0 0 0 0 0Data Consumers 36 12 12 12 data consumers 155 0 46 89 0

Assumption Made to GenerateEstimate

• System developed in Oracle• Team has completed several Oracle Projects• Team has completed several projects of this type• Team has experience in this industry•• Requirements are stable?Requirements are stable?

Estimate At SRASRA Estimate

Function Points FP/Person

Month

Defects/Function

Points819 14.3 0.18

ActivitySystem

Designers/Analysts

Prog.Test

Engrs.Project

Mgt.QA/CM

TechPubs

Total Hours

Activity Length (Days)

Start Dates

End Dates

Requirements Analysis 958 0 451 107 155 63 1733 54 6/1/2000 7/25/2000

Preliminary Design 725 225 283 92 113 54 1490 81 6/19/2000 9/9/2000Detail Design 1087 337 424 138 169 81 2235 118 7/26/2000 11/21/2000Code and Unit Test 61 359 90 26 94 14 643 104 9/17/2000 12/30/2000Integration and Test 343 229 571 68 382 69 1662 119 10/18/2000 2/14/2001System Integn & Test 190 68 195 27 152 27 659 296 6/1/2000 3/24/2001Installation 155 56 89 18 100 18 436 163 10/27/2000 4/8/2001Total 3519 1273 2102 475 1164 326 8859 311 6/1/2000 4/8/2001

Function Point Count at SDS124 47 25 54 0 1435 1282 533 254 95 400 0

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Data Encryption 5 5encryp any standard phone inputs if international 22 0 0 37 0

0 0 0 0 0Ad HOC report Writer 3 6 1 1 13 32 4 7 0

0 0 0 0 0

error notification 14initial error notification and correction notification 0 76 0 0 0

0 0 0 0 0

data push 21 7 7initiate data correction to providers 90 38 0 52 0

data pull 21 7 7initiate data correctionfrom consumers 90 38 0 52 0

Assumption Made to GenerateEstimate

• System developed in Oracle• Team has completed several Oracle Projects• Team has completed several projects of this type• Team has experience in this industry•• Requirements are stable?Requirements are stable?

Estimate At SDSSDS Estimate

Function Points

FP/Person Month

Defects/Function

Points1,436 14.1 0.19

ActivitySystem

Designers/Analysts

ProgrammersTest

Engrs.Project

Mgt.QA/CM

TechPubs

Total HoursActivity Length (Days)

Start Dates

End Dates

Requirements Analysis 1699 0 800 190 274 111 3074 68 6/1/2000 8/8/2000

Preliminary Design 1297 402 506 165 201 96 2667 100 6/26/2000 10/4/2000Detail Design 1945 603 759 247 302 145 4000 145 8/12/2000 1/4/2001Code and Unit Test 104 611 153 45 160 23 1095 131 10/13/2000 2/21/2001

Integration and Test 617 411 1029 122 688 124 2991 151 11/21/2000 4/21/2001

System Integn & Test 342 122 350 48 272 49 1185 371 6/1/2000 6/7/2001

Installation 277 99 159 32 179 32 777 204 12/3/2000 6/25/2001Total 6281 2248 3754 847 2077 581 15788 389 6/1/2000 6/25/2001

Function Points for Estimate Tab

16 3 8 8 0 196 175 69 16 30 59 0

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Model 2 1 2 2 9 5 8 15 0Equation 1 0 5 0 0 0Increment Phasing 2 1 1 1 9 5 4 7 0Increment Breakage 2 1 1 9 0 4 7 0Labor Cost 2 1 1 9 0 4 7 0APM 3 1 1 13 0 4 7 0MN APM 3 1 1 13 0 4 7 0Description 2 1 1 9 0 4 7 0

8 17 9 5 0 221 197 34 92 34 37 0

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New Estimate 1 1 4 0 0 7 0Open Estimate 1 0 0 4 0 0Save Estimate 0 0 0 0 0Save Estimate As 1 4 0 0 0 0Copy Estimate 0 0 0 0 0Close Estimate 0 0 0 0 0Load Model 1 1 4 0 0 7 0Import Comands 1 1 4 0 0 7 0Save Commands as 1 1 4 0 4 0 0Exit 0 0 0 0 0 0 0 0 0 0Component List 1 0 0 4 0 0Component Tree View 1 0 0 4 0 0Estimate List 1 0 0 4 0 0Window List 1 0 0 4 0 0Create Component Window 0 0 0 0 0Close Reports for Other Estimates 0 0 0 0 0Close All Reports 0 0 0 0 0

0 0 0 0 0Reports 16 0 86 0 0 0

0 0 0 0 0Constrain Project 2 1 1 1 9 5 4 7 0

0 0 0 0 0Set Default Model 1 1 1 4 0 4 7 0Start with empty estimate 0 0 0 0 0reset preferences 0 0 0 0 0Help 1 0 0 4 0 0

Function Points for COSTAR

Function Points

Component #

Component Name

ComponentSummary inp

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1 Estimate TAB196 77 18 34 66 0

2Component TAB 202 77 24 34 66 0

3 Menu Items221 39 103 38 41 0

Total 618 193 145 106 174 0