SOFTWARE ESTIMATING 2

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SOFTWARE ESTIMATING 2

• MN3309 Session 5
• Prof. Mark Nissen

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Agenda

• Estimating Methods Revisited
• CoCoMo II Revisited
• Function Points
• Web Software Example
• Summary

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Importance of Software Estimates

• Estimates drive all project planning
• Funding levels phasing
• Oversight reviews
• Contract requirements data
• Poor estimates --gt project failure
• Cost schedule overruns
• Crisis mode operations
• Sacrificing quality to buy schedule
• Basis of comparison for actuals

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Estimating Methods

• CSAWS - important to understand
• Analogy - similar programs
• Expert opinion - ROM grass roots
• EVM (C/SCS) extensions
• Parametric model - COCOMO, SLIM
• Functionality - Function/feature points
• Timebox
• Set max cost schedule, prioritize rqmts
• Deliver functionality at threshold (RAIV?)

5
CoCoMo II

• Estimates
• S/W cost mm f(KDSI)bgt1 scale?
• S/W schedule f(cost) 0ltblt1
• Parameters multiplicative (0.09 - 9.42)
• Use for projects
• Sensitivity analysis important
• Calibration is essential
• Problems with CoCoMo II
• Not developed for Web apps
• Estimates driven by SLOC count

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Function/Feature Points

• Language-independent approach
• Count S/W functions/features
• Adjust for environment/complexity
• Use to estimate SLOC
• Advantages over other methods?
• Timing of estimates?
• Accuracy of estimates?
• Reliability of estimates?
• C-SAWS estimates
• Can integrate with CoCoMo II

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Function Point Classes
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Function/Feature Points

• Count 5 S/W attributes
• Internal file (IF) - used/maintained by app
• External interface file (EIF) - shared IF
  External input (EI) - change data in IF
• External output (EO) - report, message
• External inquiry (EQ) - I/O w/o update
• 14 complexity adjustments
• Feature points include algorithms
• Use for real-time systems

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Web Software Example

• Web site has many pages (IOC)
• New addition (FOC)
• Create using word processor, ftp to site
• 10 pages (static) - 10 IF, 10 EQ
• 1 image (x10) - 10 IF
• 10 links to external sites (x10) - 100 EQ
• 10 links from IOC app (x10) - 0 EIF
• Consistency
• Important to be consistent in counting
• Ensure common interpretation/measure

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Counting Example
(0) (0) (10)
(0) (0) (0) (100)
(20)
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Counting Example
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Adjustment Example

• Adjustments (SEF 14)
• Back-up recovery - 0
• Data communication - 0
• Distributed processing - 0
• Critical performance - 1
• Heavy-use config - 1
• Online data entry - 0
• Transaction complexity - 0

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FP Adjustments (Cont)

• Adjustments (cont)
• Online file update - 0
• Complex external processing - 0
• Complex internal processing - 0
• Reusability - 2
• Installation factor - 2
• Multiple sites - 2
• Change facilitation (maint) - 2
• Adj (10 x 0.01 0.65) 0.75
• AFP 470 x 0.75 353

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SLOC Estimates

• Backfire conversion
• Code generator (16 SLOC/FP) 5648
• RAD (4 SLOC/FP) 1412
• Quasi-SLOC approach
• 10 pages _at_ 80 lines 800
• 10 images _at_ 10 lines 100
• 100 links _at_ 1 lines 100
• Total 1000
• Timebox approach
• 15P x 4H x 9W x 8SLOC/H 4320

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Summary

• Estimates drive all project planning
• Many methods available
• Problems with CoCoMo II
• Advantages of function points
• Consistency important in counting FPs
• Can be adapted to Web software
• Triangulate between multiple methods