Sizing Your Development Effort Using Function Point Analysis Mike Pasley Logic Central .

Sizing Your Development Sizing Your Development Effort Using Function Point Effort Using Function Point

AnalysisAnalysis

Mike PasleyMike Pasley

Logic CentralLogic Central

http://www.logicentral.comhttp://www.logicentral.com

Function Point AnalysisFunction Point Analysis

C/S Order Entry System

• Proposal: planned budget-$100k, schedule-18 Mos

• Common scenario: $150k, 24Mos– Pre-release bug fixes: $50k– Post-release bug fixes: $25k

• Unhappy Customers, sales personnel

• Going to competition

• Lost Business: another $200k


C/S Order Entry System

• Does Not Have To Be That Way!!• Other companies, same application

– $75k or less, 16 Mos– All Defect Removal: $15k

• What are they doing differently?– 5 Steps to Software Quality Control

• (Applied Software Measurements - Capers Jones)


5 Steps

• Establish Software Quality Metrics Program

• Establish Tangible Performance Goals

• Establish Meaningful Software QA

• Develop Leading Edge Corporate Culture

• Determine SW Strengths & Weaknesses

Where to begin?

Function Point AnalysisFunction Point AnalysisHow would you build a house?


What Is Function Point Analysis?

• Synthetic metrics derived from enumerating and weighing five external attributes of software applications:– Inputs

– Outputs

– Inquiries

– Internal Logical Files

– External Interface Files

Plus Factor: index of system's overall complexity


What Is Function Point Analysis?

• Function points are indicators of size based on the 'logical' view of a piece of software.

• Make it possible to measure the size of information systems according to what the user sees and interacts with– Quantify functionality delivered to user based

primarily on logical design


Summary of Benefits

• Scheduling, effort, cost estimates– Easier– Greater Accuracy

• Improves communications, sharpens management judgement, improves development process

• GUI, Algorithms, Objects


Who Needs Function Points

• Anyone who has responsibility for estimating and sizing software or measuring productivity

• Anyone who is responsible for setting and meeting customer expectations for software projects


FPA fits Engineering Method

• Use of heuristics (a decision-making aid) to cause the best change in a poorly understood system given available resources


Engineering Method Steps

• Identify Problem• Gather Information• Search for Creative

Solutions• Do Preliminary

Design

• Select Preferred Solution

• Prepare plans, specifications, reports

• Implement


Agenda

• Fundamentals Involved: 20 Minutes

• Simple Example: 10 Minutes

• Using Results: 10 Minutes

• Current Issues: 5 Minutes

• Reference Materials: 5 Minutes

• Questions & Answers: 10 Minutes


Development Goals

• Software should be completed

• Software should work


Relationship Goals

• Clients should be satisfied

• Developers should be satisfied

• Clients/Developer relationship should be trusting, respectful


Connections • If everyone understands size of project , all

parties will work better together• Three blind men/elephant effect:

– One near the tail described it as a snake

– One near the leg described it as a tree trunk

– One near the side described it as a wall

– Each description gives an accurate picture of some aspects of the elephant, but a false picture of the elephant as a whole.


User Viewpoint• Productivity: “Goods or services produced per

unit of labor or expense”

• Customers do not buy lines of code• Customers care about functionality• Focus: “What” is being delivered without

clouding the issue with “how” it is being done.– User business function and exists for business reasons

not just for technical or design reasons


Terminology

• Application Boundary

• Inputs

• Outputs

• Inquiries

• Internal Logical Files

• External Interface Files


Application Boundary

• Drawn around entire application

External Interface Files

Internal Logical Files

Inquiries

Input Output

Boundary


External Inputs (EI)

• An elementary process in which data crosses the boundary from outside to inside.– Data input screen

– Electronically

– Another application

– Business data: does update internal logical file

– Control data: does not update internal logical file


External Outputs (EO)

• An elementary process in which derived data passes across the boundary from inside to outside.– Creates reports– Creates output files sent to other applications– Created from internal logical files/external

interface file


External Inquiries (EQ)

• An elementary process with both input and output components that result in data retrieval from one or more internal logical files and external interface files

• Sent outside the application boundary– Input process does not update ILF– Output side does not contain derived data



• A User identifiable group of logically related data that entirely within the applications boundary and is maintained through External Inputs


External Interface Files (EIF)

• A User identifiable group of logically related data that is used for reference purposes only.– Resides entirely outside application– Maintained by another application– It is an ILF for another application






Inquiries

Input Output

Boundary


General System Characteristics

• Data communications

• Distributed functions

• Perfomance objectives

• Heavily used configuration

• Transaction rate

• On-line data entry

• End-user efficiency

• On-line update

• Complex processing

• Reusability

• Installation ease

• Operational ease

• Multiple sites

• Facilitate change


Complexity of Files

• Data Element Type (DET)• A unique user recognizable field from a business

perspective which participates in a transaction or is stored on a logical data file.

– Includes radio buttons, check boxes, command buttons, static images, and sound bytes

• Record Element Type (RET)– A user recognizable subgroup of data elements within

an ILF or EIF. (orders types)


Determining File Complexity

RET DET 1 -19 DET 20 -50 DET 51+1 LOW LOW LOW2 -5 LOW AVG HIGH6+ AVG HIGH HIGH


Complexity of Transactions

• The complexity of an transaction is determined by counting the number of logical File Types Referenced (FTRs) and the number of Data Element Types.


Complexity of Outputs

FTR DET 1-4 DET 6-19 DET 20+

0 -1 LOW LOW AVG

2 -3 LOW AVG HIGH

4+ AVG HIGH HIGH


Complexity of Inputs

FTR DET 1-4 DET 5-15 DET 16+

0 -1 LOW LOW AVG

2 LOW AVG HIGH

3+ AVG HIGH HIGH


Complexity of Inquiries• Determined by using the more complex of

its input and output components (usually this is the output component).


The total function points for the system are then determined by counting the number of elements with each type and complexity and applying a weighting factor according to the following table:

Element 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


File ComplexityFILE NAME FILE TYPE RET DET COMPLEXITY

Order File ILF 1 70 Average

Agent File EIF 1 5 Low


Transaction ComplexityTRANSACTION TYPE FTR DET COMPLEXITY

Screen Display EQ 2 73 High

Edit EI 1 68 Average

Error Messages EO 1 3 Low


The total function points for the system are then determined by counting the number of elements with each type and complexity and applying a weighting factor according to the following table:

Element Low Average High

EI 0 X 3 1 X 4 0 X 6

EO 1 X 4 0 X 5 0 X 7

EQ 0 X 3 0 X 4 1 X 6

ILF 0 X 7 1 X 10 0 X 15

EIF 1 X 5 0 X 7 0 X 10


Results• Unadjusted total: 29 function points

• Total then adjusted by a ranking of 0 to 5 to each of the 14 general system characteristics

• Maximum possible score of 70 for the general system characteristics (5 x 14).

• Formula: [.65 + (.01 x GCS score)] * Unadjusted Total

• Count can vary a maximum of 35% above or below the unadjusted count


Results

• Do The Sanity Check!!!– Validate Results

• Team Review

• All Components Included?

• User Viewpoint Only


Summary

• User Viewpoint

• Application Boundary– Transactions

• Inputs

• Outputs

• Inquiries

– Files

• Internal

• External


User Viewpoint• Productivity: “Goods or services produced per

unit of labor or expense”

• Customers do not buy lines of code• Customers care about functionality• Focus: “What” is being delivered without

clouding the issue with “how” it is being done.– User business function and exists for business reasons

not just for technical or design reasons






Inquiries

Input Output

Boundary


Benefits of Function Points

• Scheduling, effort, cost estimates

• Effects on communications, sharpens management judgement, improves development process

• GUI, Algorithms, Objects


Gather Documentation• Users’ perceived objectives, problems and needs.

• Documentation regarding the current system,

• Refined objectives and constraints for the proposed system.

• Requirements documentation

• All Window and Report Layouts

• Interfaces with other systems

• Logical and/or preliminary physical data models


Economic Applications• Production

– FP per person-month

– Work/hrs per FP

– $Dev per FP

– $Maint per FP

• Consumption– FP owned by

enterprise

– FP needed by end users

– Build, lease, or purchase

– Contract vs In-House

– Value Analysis

Quality• Test cases per

FP

• Defects discovered per FP

• Defect Potential per FP

• Defect Removal per FP


Issues• Too prone to human misinterpretation

– the use of certification programs and exams has narrowed the range of counting variance to within about 10 percent.

• Too labor-intensive

– automated counting tools • Not adequate for non- business information systems

– consumer devices , real -time, embedded– Continually revised, adapted (feature points, Engrg , object, etc)

• Standardization

– 20 variations , IFPUG dominant– International Standards Organization

Function Point AnalysisFunction Point AnalysisWhere to get more information and

presentation references• Int’l Function Point User Group (www.ifpug.org)• Software Productivity Research (www.spr.com)• Longstreet Consulting (www.ifpug.com)• Geneer (www.geneer.com)• Capers Jones Books on Software Quality

– Software Quality, Analysis & Guidelines– Applied Software Measurement


Questions ????


Contact Information

Mike PasleyEmail Address: [email protected] Central Web Page: http://www.logicentral.com

Sizing Your Development Effort Using Function Point Analysis Mike Pasley Logic Central .

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