1. Software Size Measures for Cost Estimation
CSCI 577a
Software Engineering I
Fall 2017
Kan Qi, USC

2. Outline The Commonly Used Size Metrics Effort Estimation
Local Calibration
Workshop
11/06/2017
©USC-CSSE

3. Software Size Measures
Source Lines of Code (SLOC)
Function Points (FP)
Use Case Points (UCP)
Story Points
11/06/2017
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4. COCOMO Effort Formulation
# of cost drivers
Effort (person-months) = A (Size)E P EMi
i=1
Where:
A is a constant derived from historical project data (currently A = 2.94 in COCOMOII.2000)
Size is in KSLOC (thousand source lines of code), or converted from function points or object points
E is an exponent for the diseconomy of scale dependent on five additive scale factors according to b = *SSFi, where SFi is a weighting factor for ith scale factor
EMi is the effort multiplier for the ith cost driver. The geometric product results in an overall effort adjustment factor to the nominal effort.
11/06/2017
©USC-CSSE

5. Software Estimation Accuracy4x 2x
Relative Size Range x
0.5x
SLOC
0.25x
Feasibility
Plans/Rqts.
Design/Architecture
Develop and Test
Need Estimates Here
Phases and Milestones
11/06/2017
©USC-CSSE

6. Function Points EIF EI EI EO EO EQ EQ ILF EI EO EQ 11/06/2017
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7. Function Points (1/3) Data Functions: Transaction Functions: L : low
EI – External Input
EO – Ext. Output
EQ – Ext. Queries
Classified by:
DET – Data Element Type
FTR - File Type Referenced
Data Functions:
Data Function:
ILF – Internal Logical File
EIF – External Interface File
Classified by:
DET – Data Element Type
RET - Record Element Type
L : low
A:average
H: high
9/19/2016
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8. Function Points (1/3)
11/06/2017
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9. Function Points (2/3) General System Characteristics
General System Characteristics Cntd.
Installation ease
Operational ease
Multiple sites
Facilitate change
Data communications
Distributed data processing
Performance
Heavily used configuration
Transaction rate
Online data entry
End-user efficiency
Online update
Complex processing
Reusability
Value Adjustment Factor (VAF)
11/06/2017
©USC-CSSE

10. Function Points (3/3) Application Function Points (AFP)
Development Function Points (DFP):
Enhancement Function Points (EFP):
11/06/2017
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11. Software Estimation Accuracy4x 2x
Relative Size Range x
0.5x
Function Points
0.25x
Feasibility
Plans/Rqts.
Design/Architecture
Develop and Test
Need Estimates Here
Phases and Milestones
11/06/2017
©USC-CSSE

12. Use Case - Written Brief Description
Bank Customer uses the ATM to withdraw money.
Actors
Bank Customer; Bank
Preconditions
There is an active network connection to the bank.
The ATM has cash available
Basic Flow
Bank Customer inserts ATM/Debit card
Validate user
ATM displays and prompts for account
Bank Customer selects account
ATM displays alternatives
Bank Customer selects withdraw option
ATM prompts for amount
Bank Customer enters an amount
ATM sends info to Bank as transaction
11/06/2017
©USC-CSSE

13. Use Case – Written Cntd. Basic Flow Money is dispensed
ATM/Debit card is returned
Receipt is printed
Alternative Flows
2a. If user is not validated, then return error
8a. If Bank Customer enters an amount that cannot be created with the type of cash in the ATM machine, display a message that amount must be in multiple of 20. Ask Bank Customer to re-enter amount.
8b. If Bank Customer enters an amount that exceeds the withdrawal limit, display warning message and ask Bank Customer to re-enter amount.
8c. If Bank Customer enters an amount that exceeds the amount available in account, return warning message and ask Customer to re-enter. …
11/06/2017
©USC-CSSE

14. Use Case - Diagram Withdraw Cash Transfer Funds Deposit Funds
Bank Customer
Deposit Funds
Bank
Refill Machine
Maintenance Person
11/06/2017
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15. Use Case Points (1/4) Use Case Complexity # of Transactions Weight
Simple
3 or fewer 5
Average
4 to 7 10
Complex
More than 7 15
Unadjusted Use Case Weight(UUCW):
Actor Complexity
Actor Type
Weight
Simple
System through API 1
Average
System through protocol
Person through text-based interface 2
Complex
Person through GUI 3
Unadjusted Actor Weight(UAW):
11/06/2017
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16. Use Case Points (2/4) Tech-nical Factor Description Weight T1
Distributed System 2 T2
Performance Objectives T3
End-user Efficiency 1 T4
Complex Processing T5
Reusable Code T6
Easy to Install
0.5 T7
Easy to Use
Tech-nical Factor
Description
Weight T8
Portable 2 T9
Easy to Change 1
T10
Concurrent Use
T11
Security
T12
Access for 3rd Parties
T13
Training Needs
For each of the 13 Factors, assess the project and rate from 0 (irrelevant) to 5 (very important).
Impact of each factor = Impact Weight (W)× Rated Value (A)
11/06/2017
©USC-CSSE

17. Use Case Points (3/4) Environ-mental Factor Description Weight E1
Familiar with Development Process
1.5 E2
Application Experience
0.5 E3
Object-Oriented Experience 1 E4
Lead Analyst Capability E5
Motivation E6
Stable Requirements 2 E7
Part-time Staff -1 E8
Difficult Programming Language
For each of the 8 Factors, assess the project and rate from 0 (irrelevant) to 5 (very important).
Impact of each factor = Impact Weight (W)× Rated Value (A)
11/06/2017
©USC-CSSE

18. Use Case Points (4/4) Unadjusted Use Case Point(UUCP)
Unadjusted Use Case Weight (UUCW) +
Unadjusted Actor Weight (UAW)
Technical Complexity Factor (TCF)
Environment Complexity Factor (EF)
Use Case Points
UUCPx TCF x EF
11/06/2017
©USC-CSSE

19. Software Estimation Accuracy4x 2x
Relative Size Range x
0.5x
Use Case Points
0.25x
Feasibility
Plans/Rqts.
Design/Architecture
Develop and Test
Need Estimates Here
Phases and Milestones
11/06/2017
©USC-CSSE

20. Agile Methodology
11/06/2017
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21. User Stories Structure Example
As a <Type of User>, I want <To Perform Some Task>, So that <I can achieve some Goal / Benefit / Value>
As a Customer, I want to withdraw cash from an ATM, So that I don’t have to wait in line at the Bank
11/06/2017
©USC-CSSE

22. Story Points Planning Poker Development Team Planning Poker Cards
Fibonacci Series (1, 2, 3, 5, 8, 13, 21, …)
Estimate Relative Effort
11/06/2017
©USC-CSSE

23. Software Estimation Accuracy4x 2x
Relative Size Range x
0.5x
Story Points
0.25x
Feasibility
Plans/Rqts.
Design/Architecture
Develop and Test
Need Estimates Here
Phases and Milestones
11/06/2017
©USC-CSSE

24. Software Estimation Accuracy4x 2x
Relative Size Range x
Use Case Points
0.5x
Function Points
Story Points
SLOC
0.25x
Feasibility
Plans/Rqts.
Design/Architecture
Develop and Test
Need Estimates Here
Phases and Milestones
11/06/2017
©USC-CSSE

25. Effort Estimation SLOC Use Case Points Function Points Story Points
Empirically calibrated model, e.g. COCOMO II.
Use Case Points
20 person-hours per UCP
Function Points
4 ~ 15 person-hours per FP
Story Points
Decided based on the referenced task
11/06/2017
©USC-CSSE

26. Local Calibration Productivity Index Simple Linear Regression
Using the productivity of past projects to estimate the effort of the current project size.
The most simple but widely used.
Simple Linear Regression
Building a simple regression model to explain the linear relationship between a size metric as the predictor and effort (PM) as the response.
The Bayesian approach to combine domain knowledge and empirically calibrated results.
Used in COCOMO II’s calibration.
11/06/2017
©USC-CSSE

27. Evaluation Criteria Coefficient of determination (R^2) :
Used to evaluate goodness of fit.
Mean Magnitude Relative Error (MMRE) :
Used to evaluate predication accuracy
Commonly accepted criterion: MMRE <= 25%
Percentage Relative Error Deviation (PRED)
Used to evaluate predication accuracy.
Commonly accepted criterion: PRED(.25) >= 75%
11/06/2017
©USC-CSSE

28. References
[1] Anandi Hira, Alternative Size Measures for Software Estimation
[2]Ray Madachy, Capability Maturity Model – Integrated (CMMI)
11/06/2017
©USC-CSSE

29. Workshop
Choose a use case and apply the counting process of UCP to evaluate UUCW, UAW, TCF, and EF to Calculate UCPs. ~ 12 minutes.
Present your counting results and estimated effort for this use case. ~ 3-5 minutes.
Briefly introduce the use case you choose.
Present the evaluation results.
How many person-hours are estimated.
Do you think the estimate is in line with your experience?
11/06/2017
©USC-CSSE