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Size Estimation using UCP

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Objectives

•To describe relevance of Size Estimation•To understand the concepts and mechanics of

Use Case Point (UCP) Estimation

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Assumptions

•Familiar with Estimation concepts•Familiar with WBS Estimation and other

techniques•Familiar with Use Case Modeling concepts and

terminology

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Agenda

•Estimation - Introduction•Relevance of Size Estimation•Why Use Case Point (UCP)Estimation?•Use Case Point Estimation framework task

workflow

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Estimation - Introduction

• What are Estimates?• Bottom Up (grassroots or engineering) Estimates

• WBS based estimates.

• Top Down Estimates• Not WBS based. (Function Point, Object Point, Use Case Point,

COCOMO)

• Best Practices for Estimation• Combine estimates from different experts and estimation

strategies• Estimate top-down and bottom-up independently• Justify and criticize estimates

• Use method based estimates to improve expert estimates

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Relevance of Size Estimation

•Why do we need Size Estimates?• To support planning, budgeting and monitoring

activities• To verify project viability• To elaborate technical and commercial proposals• To get early and precise effort estimates

•SEI-CMMI model mandates use of size estimation as basis for Effort, Schedule and Cost Estimation.

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What is UCP?

Use Case Point (UCP) Size Estimation•A method for estimating software development

effort based on use cases•The Use Case Point (UCP) estimation method

was introduced by Gustav Karner in 1993•It is inspired by Function Point Method•It defines the functional scope of the system to

be developed. The functional scope is the basis for top down estimation.

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How is it Calculated?

• Classify Actors• Classify Use Cases• Define Technical Complexity Factors• Define Environmental Factors• Calculate Use Case Points (UCPs)

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Estimation Framework Task flow

Classify Actors Compute Unadjusted Actor Weight (UAW)

Classify Use CasesCompute Unadjusted

Use Case Weight (UUCW) based on Transactions or

Analysis ClassesCompute Unadjusted

Use Case Points

Compute Environment Factor (Efactor)

Arrive at Use Case Points (UCPs)

Arrive at Productivity Index Arrive at Effort Estimate

Compute Technical Complexity Factor

(Tfactor)

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Level Of Effort

•Effort Estimation = Software Size * Productivity Index

UCP * Productivity Index•Size is independent of platform•Productivity Index is dependent on platform

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Few points to note

•Issues•No formal standard for use case writing•Dependent on well written, well structured

use cases•Technical and the Environmental Factors

have a high impact on the estimate•Combine similar actors in to one super actor•Ignore include and exclude use cases

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Advantages

•UCP is easy to Use•UCP method is User-Friendly

• Basis for object-oriented implementation• Can be measured very early in the lifecycle

•Use Cases makes more sense to users• User centered (more robust, what rather than how)

•Does not call for additional analysis

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Advantages …

• Use case modeling is increasingly being used as a method of choice to describe requirements and as a basis for design, development, testing, deployment, configuration management and maintenance.

• UCP based estimates are found to be close to actuals when estimation is performed by experienced people

• UCP may support expert knowledge when a use case model for the project is available

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Summary

•Relevance of Size Estimation•Why Use Case Point (UCP) Size Estimation?•UCP framework task flow•Advantages of UCP

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Thank You

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Actors Classification

Simple Actor

Average Actor

Complex Actor

Another System with a defined APIWeighting Factor: 1

Another System interacting through a ProtocolWeighting Factor: 2

Person interacting through GUIOr a Web-Page

Weighting Factor: 3

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Unadjusted Actor Weight Computation

Actor Type

Description Factor

Number of Actors

Actor Weight

Simple Another System with defined API

1

Average Another system interacting through a Protocol such as TCP/IP

2

Complex

A person interacting through a GUI or a web page

3

Unadjusted Actor Weight (UAW)

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Use Cases Classification

Simple Use Case

Average Use Case

Complex Use Case

Transaction is an action (step) in the scenario

<= 3 TransactionsWeighting Factor: 5

4 to 7 TransactionsWeighting Factor: 10

>= 8 TransactionsWeighting Factor: 15

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Use Cases Classification …

Simple Use Case

Average Use Case

Complex Use Case

<= 5 ClassesWeighting Factor: 5

5 to 10 ClassesWeighting Factor: 10

>= 10 ClassesWeighting Factor: 15

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Unadjusted Use Case Weight Computation

Use Case Type

Description Factor

Number of Use Cases

Use Case Weight

Simple <= 3 Transactions / Key scenarios or <= 5 Analysis Classes

5

Average 4 to 7 Transactions / Key scenarios or 6 to 10 Analysis Classes

10

Complex > 7 Transactions / Key scenarios or > 10 Analysis Classes

15

Unadjusted Use Case Weight (UUCW)

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UCP Calculations

•Unadjusted Use Case Points (UUCP)

= UAW + UUCW

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Technical Complexity Factor (TCF)Factor

Description Weight

Assigned Value (0 to 5)

Calculated factor

T1 Distributed System 2.0T2 Response time or throughput

performance objectives1.0

T3 End user efficiency 1.0T4 Complex internal processing 1.0T5 Code must be reusable 1.0T6 Easy to install .5T7 Easy to use .5T8 Portable 2.0T9 Easy to change 1.0

T10 Concurrent 1.0T11 Includes special security

objectives1.0

T12 Provides direct access for third parties

1.0

T13 Special user training facilities are required

1.0

Total Technical Factor (Tfactor)

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Environment Factor (EF)Factor

Description Weight

Assigned Value (0 to 5)

Calculated factor

F1 Familiar with the project model that is used

1.5

F2 Application experience .5

F3 Object-oriented experience 1.0

F4 Lead analyst capability .5

F5 Motivation 1.0

F6 Stable requirements 2.0

F7 Part-time staff -1.0

F8 Difficult programming language -1.0

Total Environment Factor (Efactor)

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UCP Calculations

•Technical Complexity Factor (TCF) = 0.6 + (0.01 x Tfactor)

•Environment Factor (EF)= 1.4 + (-0.03 x Efactor)

•Adjusted Use Case Points (UCP)= UUCP x TCF x EF

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Productivity Index

•Productivity Index (PI) for J2EE applications= 20 to 30 Hrs / UCP

•Karner Proposed 20 Staff Hours per UCP•Estimated Effort = UCP x PI

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