usecase based estimation

8/7/2019 UseCase Based Estimation

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Use case Based Estimation


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Actors and Goals

Use case' implies 'the ways in which a user

uses a system

Actors are people or computer systems,interacts with the S.U.D

primary actor

secondary actor

Purpose of a use case is to meet the

immediate goal of an actor


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Use Case Model

Use case diagram depicts a static view of the systemfunctions, their static relationships with externalentities

Scenario is a use case instance

Specific sequence of actions that illustrates behaviors

Main success scenario describes what happens in the mostcommon case when nothing goes wrong

Activity diagram imparts a dynamic view of thosefunctions


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The Use Case Points Method

Classifying Actors

Classifying Use Cases

Technical and Environmental Factors Producing Estimates Based on Use Case Points


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Classifying Actors

Classify the actors as simple, average or complex

Actor type: Simple, weighting factor 1

Actor type: Average, weighting factor 2

Actor type: Complex, weighting factor 3

total unadjusted actor weights (UAW) is calculated

by counting actors there are of each kind (by degree

of complexity), multiplying each total by its weighting

factor, and adding up the products.


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Use case Complexity

Weighting Factor:

Simple: 3 or fewer transactions, weighting factor 5

Average: 4 to 7 transactions, weighting factor 10

Complex: More than 7 transactions, weighting factor 15

Each type of use case is then multiplied by the

weighting factor,

unadjusted use case weights (UUCW)


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Classifying Use Cases (Method2)

Another mechanism for measuring use case

complexity is counting analysis classes

Simpleuse case is implemented by 5 or fewerclasses

Average use case by 5 to 10 classes

Complex use case by more than ten classes


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Classifying Use Cases (Method2)

Each type of use case is then multiplied by the

weighting factor,

unadjusted use case weights (UUCW)


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USE CASE POINTS METHOD

UAW is added to the UUCW to get the

unadjusted use case points (UUPC):

UUCP=UAW+UUCW


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Technical and Environmental Factors

Technical Complexity Factor (TCF) is calculated

by multiplying the value of each factor (T1-

T13) by its weight and then adding all these

numbers to get the sum called the TFactor.

TCF=0.6+(0.01*TFactor)


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Technical Complexity Factors Table


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Environmental Factor

Environmental Factor (EF) is calculated by

multiplying the value of each factor (F1-F8) by its

weight and adding the products to get the sum

called the EFactor.

EF=1.4+(-0.03*EFactor)


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Environmental Factor Table


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Use case points

UCP=UUCP*TCF*EF


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Producing Estimates Based on Use Case

Points

Karner proposed a factor of 20 staff hours per

use case point for a project estimate.


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Case Study

Internet application for a major bank

Software solution was to improve communicationbetween customers and their contacts by enabling users

to upload news, download documents and view currentactivities The development team consisted of fiveprogrammers and one technical supervisor who wasresponsible for analysis and testing. The application wasbuilt using a standard three-layer model with apresentation layer, application layer and a databaselayer


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Process Transaction

Manage System

Temporary Use case Diagram

Customer Admin


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Data Collection


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Calculating TCF & EF

TCF = 0.6 +(0.01*44)= 1.04

EF = 1.4 +(-0.03*16)= 0.92


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Estimate Produced with the Use Case

Points Method

Two actors are both people acting through aGUI

18 simple, 41 medium and 4 complex use cases

UUCP= 2*3+18*5+41*10+4*15=566

UCP=UUCP*TCF*EF=566*1.04*0.92

=541.54

=542

Total Efforts = 20*542

=10840StaffHrs

usecase based estimation

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