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Keypoint

Introduction

Function Point Variations

Problems with Lines of Code

What is Function Points?

Objectives of Function Points How do Function Points Overcome LOC Problems?

Uses of Function Points

When Should You Count Function Points?

Function Point Counting Cyclomatic complexity

Cyclomatic complexity example

References


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Metric - A quantifiable characteristic ofsoftware.

Measurement - The process of mapping fromreal world attributes to a mathematicalrepresentation.

Model - A mathematical relationship betweenmetrics.


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Increasingly important for softwaredevelopment is the ability to estimate theassociated cost of development early in thedevelopment process

Estimating software size is a difficult problemthat requires specific knowledge of the systemfunctions in terms of Scope Complexity Interactions

Most frequently cited sources of software sizemetrics are Lines of code

Function point analysis


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Mk II Function Points Discovered weaknesses in Albrecht's approach

Feature Points Function points were not working for all classes of

applications

3D Function Points Designed to solve two problems with Albrecht

approach


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Lack of a universally accepted definitionfor exactly what a line of code is

Language dependence (high-level versuslow-level programming languages)

It is difficult to estimate the number oflines of code that will be needed todevelop a system from information thatis available in analysis and design phases

Lines of code places all emphasis oncoding, which is only part of theimplementation phase of a softwaredevelopment project


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Function Points are a unit of measure Like an hour is to measuring time

Or an inch is to measuring distance

An unit is important to understand and to

communicate such metrics as Average Cost.


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A software application in essence is a definedset of elementary business processes.

A function point is not a screen, a report, butinstead an elementary business process.

We often count screens, reports, but theseare not function points.


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Function points are independent of thelanguage, tools, or methodologies used forimplementation (ex. Do not take intoconsideration programming languages,DBMS, or processing hardware)

Function points can be estimated early inanalysis and design

Since function points are based on thesystem users external view of the system,

non-technical users of the software systemhave a better understanding of whatfunction points are measuring


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Measure productivity (ex. Number of functionpoints achieved per work hour expended)

Estimate development and support (cost benefitanalysis, staffing estimation)

Monitor outsourcing agreements (Ensure that the

outsourcing entity delivers the level of support andproductivity gains that they promise) Drive IS related business decisions (Allow decisions

regarding the retaining, retiring and redesign ofapplications to be made)

Normalize other measures (Other measures, suchas defects, frequently require the size in functionpoints)


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You cannot manage internally what you donot measure

Approximately 40% of all projects fail due tolack of management control (Coopers &

Lybrand Sept. 1995) Measurement gives you a tool to

communicate to your customers the size oftheir request, and extrapolate productivity,

quality and estimating accuracy Many competitors may already have these

insights You measure to understand and improve

your processes


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Measure functionality that the user requestsand receives

Measure software development andmaintenance independently of technology

used for implementation Simple enough to minimize the overhead of

the measurement process

A consistent measure among various

projects and organizations


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Early and often The sooner you can quantify what a project is

delivering, the sooner it is under control Under IFPUG 4.1, there are rules and guidelines

that make it possible to count function pointsonce the requirements have been finalized

During requirements gathering the estimate ofsize in function points can be refinedcontinuously

Function points should be recountedthroughout the development process andcounts can be compared to measure scopecreep and breakage


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Determine the type of function pointcount

Identify the counting scope andapplication boundary

Determine the Unadjusted Function PointCount

Count Data Functions

Count Transactional Functions Determine the Value Adjustment Factor Calculate the Adjusted Function Point

Count


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Is a structured technique of classifying

components of a system. Is a method to break systems into smaller

components, so they can be betterunderstood and analyzed.

Measures software by quantifying itsfunctionality provided to the user basedprimarily on the logical design.

Logical functionality from a sophisticated(experienced) user view rather than a physicalview.


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A standard method for measuring softwaredevelopment from the customers point ofview.


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Improves requirements documentation Improves the estimating process

Improves the communication of workload

Improves the understanding of businessfunctions

Improves traceability of requirements throughImplementation

Improves the allocation of resources


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A software metric used to measure thecomplexity of software.

Developed by Thomas McCabe in 1976.

The cyclomatic complexity of a section ofsource code is the count of the number oflinearly independent paths throughthe source code.
http://en.wikipedia.org/wiki/Control_flowhttp://en.wikipedia.org/wiki/Source_codehttp://en.wikipedia.org/wiki/Source_codehttp://en.wikipedia.org/wiki/Control_flow


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For instance, if the source code contained nodecision points such as IF statements or FORloops, the complexity would be 1 since there isonly a single path through the code.

If the code had a single IF statementcontaining a single condition there would be

two paths through the code, one path wherethe IF statement is evaluated as TRUE and onepath where the IF statement is evaluated asFALSE.


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Mathematically, the Cyclomatic Complexityofa structured program is defined with

reference to a directed graph containingthe basic blocks of the program, with an edgebetween two basic blocks if control may passfrom the first to the second (the control flow

graphof the program).
http://en.wikipedia.org/wiki/Structured_programminghttp://en.wikipedia.org/wiki/Directed_graphhttp://en.wikipedia.org/wiki/Basic_blockhttp://en.wikipedia.org/wiki/Basic_blockhttp://en.wikipedia.org/wiki/Directed_graphhttp://en.wikipedia.org/wiki/Structured_programming


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The complexity is then defined as:M = EN + 2P

whereM= cyclomatic complexity

E= the number of edges of the graph

N= the number of nodes of the graph

P= the number ofconnected components
http://en.wikipedia.org/wiki/Connected_component_(graph_theory)http://en.wikipedia.org/wiki/Connected_component_(graph_theory)


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An alternative formulation is to use a graph inwhich each exit point is connected back to

the entry point. In this case, the graph is said to be strongly

connected, and the cyclomatic complexity ofthe program is equal to the

cyclomatic numberof its graph (also knownas the (first Betti number), which is definedas:M = EN + P
http://en.wikipedia.org/wiki/Betti_numberhttp://en.wikipedia.org/wiki/Betti_number


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For this graph, E = 9, N = 8 and P = 1, so the cyclomatic complexityof the program is 3.

E l f


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Examples ofcyclomatic complexity

L=1, N=2, P=1

M=1-2+2=1

L=4, N=4, P=1

M=4-4+2=2

L=4, N=5, P=1M=4-5+2=1

L=2, N=4, P=2

M=2-4+4=2


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REFERENCES

Software engineering : A Practitioners

approach

5 Ed. By Roger Pressman,

Ivan sommerville.


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THANK YOU

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