Functional Point Analysis1

8/2/2019 Functional Point Analysis1

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By

Aparna Naik

www.DestinationQA.com

Software Testing and QA

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Agenda

What is Software Sizing

Need for Software Sizing Software Sizing Methodologies

Introduction to Function Point Analysis (FPA)

Process of Counting Function Points

Adjustment Factors in Function Point Analysis

Function Point Count Types Case Study



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Software Sizing



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Software Sizing

Software sizing is an activity in software engineering that

is used to estimate the size of a software application or

component in order to be able to implement other

software project management activities (such asestimating or tracking).


Size is an inherent characteristic of a piece of softwarejust like weight is an inherent characteristic of a tangible

material.
http://en.wikipedia.org/wiki/Weighthttp://en.wikipedia.org/wiki/Weight


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Need for Software Sizing



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What do you see on the Surface?

The image represents the tip of an iceberg. The real issue is not the tip, but what is under

the surface of the water and can not be seen. The same is true when you design a software

application.



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Airline Surface

This appears on the surface to be a simple inquiry, but this is extremely complex.

The process actually includes 1,000s of elementary processes, but the end user is

only exposed to a very simple process.

All possible routes are calculated, city names are converted to their internationalthree characters, interfaces are sent to all the airline carriers (each one being

unique), this is an extremely complex and robust process! When we size software

applications we want to understand what is exposed and what is under the surface.



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Need for Software Sizing


Some common reasons for sizing the software are:

1. To Measure and Manage Productivity

2. Estimation and budgeting

3. Monitoring Progress

4. Evaluating Requirements coverage for buying new Software5. Bidding for projects

6. Allocating Testing Resources

7. Risk Assessment

8. Phasing Development Work

9. Prioritizing Work

10. Software Asset Valuation11. Outsourcing Software Development, Support or Maintenance.

12. CMMi Level 2 and 3 require that a valid sizing method be used.


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Software Sizing Methodologies


Some of the common software sizing methodologies are:

1. Lines of Code (Oldest)

2. Use Case based Software Sizing

3. COSMIC - Common Software Measurement International Consortium (ISO)

4. IPFUG Function Point Analysis (ISO)

5. Mk II Function Point Analysis (ISO)


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Software Sizing Lines of Code


Historically, the most common software sizing methodology has been counting the lines ofcode written in the application source

Advantages:

1. Automation of the counting process is possible.

2. Intuitive - Can be seen and effect can be visualized.

Disadvantages:

1. Lack of Accountability - The coding phase is only 30 - 35% of the total effort.

2. Very difficult to standardize lines of code for a particular function as it heavily depends

on Skill level of the programmer, programming language, etc.3. Lack of counting standards (Do comments count? Data Declarations? etc)

Hence a more mature Sizing Algorithm was needed.


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History


The idea of measuring a size of software in terms of its functionality as opposed to

its physical components was first put forward by Allan Albrecht of IBM in 1979 He proposed a method called Function Point Analysis which has since evolved into

the IFPUG method.

The definition of this method is now managed by the International Function Point

Users Group.

Albrechts clever piece of lateral thinking laid the foundations for the subject offunctional size measurement.

The IFPUG method actually has two components, firstly concerned with a measure

of functional size and the second concerned with a measure of the contribution to

overall size of 14 technical and quality factors.

Albrechts original approach has been refined significantly over the last 30 years, butits basic concepts are unchanged from the mid 1970s.

Nevertheless, the IFPUG method is still the most widely-used FSM method, albeit

confined to the domain of business application software.


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Developments of 1st GenerationMethods


Several developments from the Albrecht/IFPUG approach have been made toimprove the size measure, or to extend its domain of applicability.

Capers Jones published a method based closely on that of Albrecht, called

Feature Points, with the aim of extending FSM to apply to scientific

algorithms. The method has been largely abandoned due to the intrinsic

difficulty of sizing mathematical algorithms

Charles Symons developed the MkII Function Point Method which aimed to

improve on Albrechts approach by better taking into account the internal

complexity of data-rich business application software.


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Continued


Scott Whitmire developed 3D Function Points to size business application and

real-time software drawing on Albrechts general approach.

The Netherlands Software Metrics Users Association (NESMA) published a

variant of the IFPUG method which aimed to simplify some of the sizing rules

The University of Qubec, Montral and others published the Full Function Point

Method which used the IFPUG rules for business application software and addedextra components for sizing real-time software.

It will be seen that all of these methods can trace their roots back to Allan Albrechts

original ideas. They are what we call 1st Generation FSM Methods.


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Function Point Analysis



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Introduction to Function Point Analysis


What is a Function Point?A function point is a unit of measurement to express the amount of business functionality

an information system provides to a user.

Some Definitions

1. Functional SizeA size of the software derived by quantifying the Functional User Requirements.

2. Functional Size Measurement (FSM)

The process of measuring Functional Size.

3. FSM MethodA specific implementation of FSM defined by a set of rules, which conforms to the

mandatory features of this part of ISO/IEC 14143. There are currently 5 ISO recognized

FSM Methods.


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Function Point Analysis - Characteristics

Function points are a unit measure for software much like an hour is to

measuring time, miles are to measuring distance


1. Measures Functional User Requirements

2. Excludesa. Physical or technical components

b. Quality features

3. Derived in terms understood by users of the software. The measure relates directly to the

business requirements, which the software is intended to address

4. Derived without reference to effort to develop or support. The Function Point technique

provides an objective, comparative measure, which assists in the evaluation, planning,management and control of software production.

5. It is a method to break systems into smaller components, so they can be better understood

and analysed.

6. It can therefore be readily applied across a wide range of development environments and

throughout the life of a development project, from early requirements definition to full

operational use.


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Function Point Unit Of Software


Function Points are the output of the software development process.

Function points are the unit of software.

It is very important to understand that Function Points remain constant regardless

who develops the software or what language the software is develop in.

Unit costs need to be examined very closely. To calculate average unit cost all items

(units) are combined and divided by the total cost.


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Unit Software example


For example, assume you are going to manufacture a computer mousepad. The total

Cost to manufacture 1,000 mousepad is $2,660. The unit cost is $2.66 (per pad).The cost break down is:

Artwork is a fixed cost at $500 (or .50 per unit)

Set Up costs are $250 (or .25 per unit)

Shipping costs are $10 (or .01 per unit) Papers for production will cost $1.50 per unit.

Rubber Pads are $ .15 per unit.

Application of paper to pad cost is $.25 per unit

Notice the variation in the unit cost for each item.One of the biggest problems with estimating software projects is understanding

unit cost. Software managers fail to break down items into similar components or

like areas. They assume all units cost the same.


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Counting Function Points



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IPFUG FSM Counting Function Points

High Level Process1. Identify Functional User Requirements. Categorize each one into one of the following types

(Base Functional ComponentsBFC):

a. Transactional Functions

i. Inputs

ii. Outputsiii. Inquiries

b. Data Functions

i. Internal Files

ii. External Interfaces

2. Rate each requirement based on complexity. Assign a Number for Function Points to each

requirement. (Unadjusted function point count)3. Determine the value adjustment factor (VAF) based on general system characteristics (GSCs).

4. Calculate the adjusted function point count. The final function point count (adjusted function

point count) is a combination of both unadjusted function point count (UFP) and the general

system characteristics (GSCs).


Function points are the units of measure used by the IFPUG Functional Size Measurement Method.


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IPFUG FSM Identify Functional Requirements


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IPFUG FSM Categorize into BFC


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Example: External Interface



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Functional point process



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External Inputs

An elementary process in which data crosses the boundary from outside to inside.

This data is coming external to the application. The data may come from a data input screen or another application.

The data may be used to maintain one or more internal logical files.

The data can be either control information or business information.

If the data is control information it does not have to maintain an internal logical file.

e.g. Data Input Fields, Error Messages, Calculated Values, Buttons



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Identify External Inputs


The following words are associated with external input orinputs.


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FTRs and DETsThe rating ofExternal Input is based upon the number of data element types (DETs) and the

file types referenced (FTRs).

File Type Referenced(FTR): A FTR is a file type referenced by a transaction. An FTR must also

be an internal logical file or external interface file.

Each internal logical file that an external input maintains is counted as an FTR

Data Element Type (DET): A DET is a unique user recognizable, non-recursive (non-repetitive)field. A DET is information that is dynamic and not static. A dynamic field is read from a file

or created from DETs contained in a FTR. Additionally, a DET can invoke transactions or can

be additional information regarding transactions.



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Rating External Inputs (EI) Example

DETsCustomer Name, Contact, Alt. Contact, Bill to, Phone, Fax, Alt. Phone, Ship To,

OK button, Cancel Button

FTRCustomer file, Contact File, Bill To file, Ship To File



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External Outputs


External Output is an elementary process in which derived data passes across the boundary

from inside to outside. Additionally, an EO may update an ILF.

The data creates reports or output files sent to other applications. These reports and files are

created from information contained in one or more internal logical files and external

interface files.


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Identify External Output


The following words are associated with ExternalOutputs


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Rating External Outputs



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Rating External Outputs Example Cnt.

There are 10 data elements

1. Days

2. Hits

3. % of Total Hits

4. User Sessions

5. Total Hits (weekday)

6. Total % (weekday)7. Total User Sessions (weekday)

8. Total Hits (weekend)

9. Total % (weekend)

10. Total User Sessions (weekend)

3 FTR1. Day Activity

2. Total Weekdays Activity

3. Total Weekend Activity



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External Inquiry (EQ)


It is 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. The input process does not update or maintain any FTRs (Internal Logical Files or

External Interface Files) and the output side does not contain derived data.


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Identify External Inquiries


The following words are associated with external

Inquiries


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Rating External Inquiry (EQ) Example



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Internal Logical File


It is a user identifiable group of logically related data that resides entirely within

the application boundary and is maintained through External Inputs.

An internal logical file has the inherent meaning it is internally maintained, it

has some logical structure and it is stored in a file.

An ILF should have at least one external output and/or external inquiry.

That is, at least one external output and/or external inquiry should include the

ILF as an FTR

An ILF should also have at least one external input.


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Rating Internal Logical Files (ILF)

The rating is based upon the number of data elements (DETs) and the record types (RETs).


RET is logical group of data with recursion

Most record element types are dependent on a parentchild relationship.


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Record Element Types

Some A are B

AAll CustomersB - Customers who havent paid in last 30 days



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Record Element Types

All B are A

AAll Customer data with Credit Card dataBCredit Card Data



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Rating ILF Example



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External Interface File


It is a user identifiable group of logically related data that is used for reference

purposes only.

The data resides entirely outside the application boundary and is

maintained by another applications external inputs.

The external interface file is an internal logical file for another application.

An application may count a file as either a EIF or ILF not both.


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Unadjusted Function Point:



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Adjustment Factors in FunctionPoint Analysis



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General System Characteristics

Definition:The value adjustment factor (VAF) is based on 14 general system

characteristics (GSCs) that rate the general functionality of the

application being counted. Each characteristic has associated

descriptions to determine the degrees of influence.

Rating:The degrees of influence range on a scale of zero to five, from no influence to strong

influence. Each characteristic is assigned the rating based upon detail descriptions provided

by the IFPUG 4.1 Manual. They ratings are:

0 - Not present, or no influence1 - Incidental influence

2 - Moderate influence

3 - Average influence

4 - Significant influence

5 - Strong influence throughout



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General System Characteristics cont

1. Data communications: How many communication facilities are there to aid in the transfer

or exchange of information with the application or system?

2. Distributed data processing: How are distributed data and processing functions handled?

3. Performance: Did the user require response time or throughput?

4. Heavily used configuration: How heavily used is the current hardware platform wherethe application will be executed?

5. Transaction rate: How frequently are transactions executed daily, weekly, monthly, etc.?

6. On-Line data entry: What percentage of the information is entered On-Line?

7. End-user efficiency: Was the application designed for end-user efficiency?



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8. On-Line updateHow many ILFs are updated by On-Line transaction?

9. Complex processing Does the application have extensive logical or

mathematical processing?

10. ReusabilityWas the application developed to meet one or

many users needs?

11. Installation ease How difficult is conversion and installation?

12. Operational ease How effective and/or automated are start-up, back

up, and recovery procedures?

13. Multiple sites Was the application specifically designed, developed, and supportedto be installed at multiple sites for multiple organizations?

14. Facilitate change Was the application specifically designed,

General System Characteristics cont



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Value Adjustment Factor (VAF)

Once all the 14 GSCs have been answered, they should be tabulated using the

IFPUG Value Adjustment Equation (VAF)



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Standard Function Point

The final Function Point Count is obtained by multiplying

the VAF times the Unadjusted Function Point (UAF). The

standard function point equation is:

FP = UAF * VAF

Where:

UAF = Unadjusted Function PointsVAF = Value Adjustment Factor



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Function Point Count Types



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Types Of Functional Point Counts



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Types of FP Counts

Development Project Function Point CountFunction Points can be counted at all phases of a development project from requirements

up to and including implementation. This type of count is associated with new

development work. Scope creep can be tracked and monitored by understanding the

functional size at all phase of a project. Frequently, this type of count is called a baseline

function point count.

Enhancement Project Function Point CountIt is common to enhance software after it has been placed into production. This type of

function point count tries to size enhancement projects. All production applications

evolve over time. By tracking enhancement size and associated costs a historical database

for your organization can be built. Additionally, it is important to understand how adevelopment project has changed over time.



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Application Function Point CountApplication counts are done on existing production applications. This baseline

count can be used with overall application metrics like total maintenance hours.

This metric can be used to track maintenance hours per function point. This is an

example of a normalized metric. It is not enough to examine only maintenance, but

one must examine the ratio of maintenance hours to size of the application to get a

true picture. Additionally, application counts can assist organizations inunderstanding the size of the entire corporate portfolio (or inventory). This type of

count is analogous to taking an inventory for a store. Like inventory, a dollar value

can be associated with any application function point count and for the entire

organization portfolio.

Types of FP Counts cont


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Uses of FPA - Software Estimation

Accuracy of a software project estimate is Predicated on a number of things :

The degree to which the planner has properly estimated the size of the product to bebuilt.

The ability to translate the size estimate into human effort, calendar time, and dollar.

The degree to which the project plan reflects the abilities of the software team.

The stability of product requirements and the environment that supports the

engineering effort.

Estimation is not merely a technique, its an art



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Size Based Estimation Model (Top Down)


In a top-down approach, the overall estimate for the project is first determined based onsome models and then the estimates for different tasks are determined.

E.g.: Function Point estimation which is a top down estimation technique is recognized as an

industry standard scientific estimation technique that is acceptable to all stakeholders


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Case Study Function PointAnalysis



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Case Study

The Weather Application

The following application was designed to capture temperature and rainfall by city and state.

There is only one input screen, one file and one report

Each field on the following input screen can be modified (add, changed or deleted). The add

and change functions are different. All previous entries viewed by using the scroll bar. Assume

a VAF of 1.0.



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Case Study


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Case Study


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Thank You


Aparna Naik

Email: [email protected]

Tel: +91 99233 50980
mailto:[email protected]:[email protected]


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Appendix


D t El t T


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Data Element Types


Radio Buttons:

Radio Buttons are treated as data element types. Within a group of, a frame, radio buttons the

user has the option of selecting only one radio button; so only one data element type is countedfor all the radio buttons contained in the frame.

Check Boxes:

Check Boxes differ from radio buttons in that more than one check box can be selected at a

time. Each check box, within a frame, that can be selected should be treated as a data element.

Command Buttons:

Command buttons may specify an add, change, delete or inquire action.

A button, like OK, may invoke several different types of transactions.

A button like next may actually be the input side of an inquiry or another

transaction.

D t El t T C t


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Data Element Types Cont


Messages:

There are three types of messages that are generated in a GUI application: error messages,

confirmation messages and notification messages.Error messages and confirmation messages:

indicate that an error has occurred or that a process will be or have been completed. They are

not an elementary or independent process alone, but they are part of another elementary process.

A message that would state, zip code is required would be an example of an error message. A

message that would state, are you sure you want to delete customer is an example of a

confirmation message. Neither type of message is treated as a unique external output, but each is

treated as a data element for the appropriate transaction.

On the other hand, a notification messages is a business type message.

For example,

you may try to withdraw from an ATM machine more money than you have in your account and

you receive the dreaded message, You have insufficient funds to cover this transaction. This is

the result of information being read from a file regarding your current balance and a conclusion

being drawn. A notification message is treated as an External Output.


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Need for Software Metrics

What does the customer want to know ?

How big is it?

How long will it take? How many people do we need?

How much will it cost?

How good is it?



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High level process



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Independence and DependenceSince the rating of transactions is dependent on both information contained in the transactions

and the number of files referenced, it is recommended that transactions are counted first. At the

same time the transactions are counted a tally should be kept of all FTRs (file types referenced)

that the transactions reference.



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ESTABLISHING THE BOUNDARYIdentify the Boundary:

Review the purpose of the function point count.

Look at how and which applications maintain data.

Identify the business areas that support the applications.

The boundary may need to be adjusted once components have been identified. In practice

the boundary may need to be revisited, as the overall application is better understood.

Function point counts may need to be adjusted as you learn about the application.Standard Documentation:

General Specification Documents

Interface Documents

Other metric reports

Interviews with the users

User Documentation Design Documentation

Requirements

Data flow diagrams


B fi d U


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Benefits and Uses:

Function Points can be used to communicate more effectively with business user groups. Function points can be used to establish an inventory of all transactions and files of a

current project or application..

Function Points can be used to size software applications. Sizing is an important

component in determining productivity (outputs/inputs), predicting effort,

understanding unit cost, so on and so forth.

Unlike some other software metrics, different people can count function points atdifferent times, to obtain the same measure within a reasonable margin of error. That is,

the same conclusion will be drawn from the results.

FPA can help organizations understand the unit cost of a software application or project.

Once unit cost is understood tools, languages, platforms can be compared quantitatively

instead of subjectively. This type of analysis is much easier to understand than technical

information. That is, a non-technical user can easily understand Function Points.

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