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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).
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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).
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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
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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
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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
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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)
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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
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The following words are associated with external
Inquiries
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Rating External Inquiry (EQ) Example
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Internal Logical File
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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).
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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
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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)
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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
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Aparna Naik
Email: [email protected]
Tel: +91 99233 50980
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Appendix
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D t El t T
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Data Element Types
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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
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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
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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.