📘 Function-Oriented Metrics (Software Measurement)

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🔹 1. Definition

Function-Oriented Metrics are software measurement techniques that evaluate software size and complexity based on the functionality delivered to the user, rather than the physical code size.

👉 In simple words: They measure what the software does, not how many lines of code it has.

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🔹 2. Key Idea ⭐

Unlike size-oriented metrics (LOC-based), function-oriented metrics focus on:

• Inputs
• Outputs
• User interactions
• Data files
• External interfaces

👉 So they are user-centric metrics.

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🔹 3. Most Common Function-Oriented Metric

🔸 Function Points (FP) 📊

Function Points measure software size based on the functional requirements provided to the user.

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🔹 4. Components of Function Points

Function Points are calculated using 5 components:

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🔸 1. External Inputs (EI)

• Data entering the system 👉 Example: User login details

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🔸 2. External Outputs (EO)

• Data leaving the system 👉 Example: Reports, invoices

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🔸 3. External Inquiries (EQ)

• Requests for data without updating system 👉 Example: Searching a record

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🔸 4. Internal Logical Files (ILF)

• Internal data stored in system 👉 Example: User database

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🔸 5. External Interface Files (EIF)

• Data used from other systems 👉 Example: Payment gateway data

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🔹 5. Function Point Formula ⭐

FP = Total Unadjusted Function Points × Value Adjustment Factor (VAF)

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🔸 Step 1: Unadjusted Function Points (UFP)

UFP = Sum of all weighted EI, EO, EQ, ILF, EIF

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🔸 Step 2: Value Adjustment Factor (VAF)

VAF = 0.65 + (0.01 × ΣFi)

👉 Fi = 14 general system characteristics (like performance, complexity, security)

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🔹 6. Example (Simple Idea)

Component	Count
Inputs	5
Outputs	4
Queries	3
Files	2
Interfaces	1

👉 These are converted into weights → FP is calculated.

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🔹 7. Advantages of Function-Oriented Metrics

✔ Language independent ✔ Focus on user requirements ✔ Better for business applications ✔ Useful in early project estimation ✔ More accurate than LOC-based metrics

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🔹 8. Limitations ❌

• Complex calculation
• Requires expert judgment
• Subjective weighting system
• Not suitable for very small programs

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🔹 9. Function-Oriented vs Size-Oriented Metrics

Feature	Function-Oriented	Size-Oriented
Basis	Functionality	Lines of Code
Unit	Function Points	LOC
Language dependence	No	Yes
Focus	User requirements	Code size
Accuracy	Higher	Lower

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🔹 10. Importance in Software Engineering

• Helps in accurate cost estimation
• Used for project planning
• Improves productivity measurement
• Helps compare different technologies fairly

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🔹 11. Key Exam Points

• Based on functionality delivered
• Main metric = Function Points (FP)
• Includes EI, EO, EQ, ILF, EIF
• Independent of programming language
• Used for early estimation and planning

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🔹 12. Short Summary

• Function-oriented metrics measure software based on user functionality
• The main technique is Function Point Analysis (FPA)
• It is more accurate and language-independent than LOC-based metrics

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🔹 13. Quick Exam Answer (2–3 lines)

Function-oriented metrics measure software size based on the functionality delivered to the user. The most common method is Function Point Analysis, which considers inputs, outputs, inquiries, files, and interfaces to estimate software size and effort.

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🔹 14. Likely Exam Questions

1. Define function-oriented metrics.
2. What are function points?
3. List components of function point analysis.
4. Differentiate between LOC and function points.
5. Why are function-oriented metrics better than size-oriented metrics?
6. What are EI, EO, EQ, ILF, and EIF?
7. Explain the importance of function-oriented metrics.