📘 Software Project Estimation: Decomposition Techniques

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🔹 1. Definition of Software Project Estimation

Software project estimation is the process of predicting the effort, cost, time, and resources required to complete a software project.

👉 In simple words: It tells us how much work, time, and money a project will need.

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🔹 2. What are Decomposition Techniques?

Decomposition techniques are estimation methods in which a project is broken down into smaller parts (modules/tasks), and each part is estimated separately.

👉 Then, all estimates are combined to get the total project estimate.

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🔹 3. Key Idea ⭐

Big Project → Small Modules → Individual Estimation → Final Total Estimate

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🔹 4. Types of Decomposition Techniques

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🔸 1. Line of Code (LOC) Based Estimation 📏

👉 Concept:

Estimate project size using Lines of Code (LOC).

🔹 Steps:

• Estimate LOC for each module
• Sum all LOC
• Convert LOC into effort using productivity rate

🔹 Formula:

Effort = LOC / Productivity

💡 Example:

• Total LOC = 10,000
• Productivity = 500 LOC/person-month 👉 Effort = 20 person-months

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🔸 2. Function Point (FP) Based Estimation ⚙️

👉 Concept:

Estimate based on software functionality.

🔹 Steps:

• Identify function components (EI, EO, EQ, ILF, EIF)
• Calculate Function Points
• Convert FP into effort

🔹 Formula:

Effort = Function Points / Productivity Rate

💡 Example:

• 200 FP / 20 FP per month = 10 person-months

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🔸 3. Object Point Estimation 🧩

👉 Concept:

Used in object-oriented systems.

🔹 Measures:

• Screens
• Reports
• Components

💡 Example:

• 50 screens + 10 reports → total object points
• Converted into effort using productivity

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🔸 4. Use Case Point (UCP) Estimation 🎯

👉 Concept:

Based on use cases and system complexity.

🔹 Steps:

• Identify use cases
• Classify complexity (simple, average, complex)
• Assign weights
• Calculate total UCP

💡 Example:

• Login system (simple) + payment system (complex)

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🔹 5. Process of Decomposition Estimation

📌 Step-by-step:

🔹 Step 1: Break Project (WBS)

Divide project into small modules

🔹 Step 2: Estimate Each Module

Use LOC, FP, or other methods

🔹 Step 3: Convert to Effort

Convert size into effort using productivity

🔹 Step 4: Combine Estimates

Add all module efforts

🔹 Step 5: Add Buffer

Include risk and contingency time

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🔹 6. Diagram Description

📊 Decomposition process looks like:

Project
  ↓
Modules (WBS)
  ↓
Individual Estimation
  ↓
Effort Calculation
  ↓
Total Project Estimate

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🔹 7. Advantages of Decomposition Techniques

✔ More accurate than top-down methods ✔ Reduces estimation errors ✔ Easy to manage large projects ✔ Helps in detailed planning ✔ Improves cost and time control

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🔹 8. Limitations ❌

• Time-consuming process
• Requires detailed project knowledge
• Difficult in early project stages
• Needs experienced estimators

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🔹 9. Top-Down vs Decomposition (Bottom-Up)

Feature	Decomposition (Bottom-Up)	Top-Down
Approach	Small to large	Large to small
Accuracy	High	Medium
Effort	High	Low
Detail level	Very detailed	General

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🔹 10. Important Exam Points

• Decomposition = divide and estimate

• Based on WBS (Work Breakdown Structure)

• Methods include:

  • LOC-based
  • Function Point
  • Object Point
  • Use Case Point

• Most accurate estimation technique

• Used for detailed project planning

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🔹 11. Short Summary

• Decomposition techniques break a project into small modules
• Each module is estimated separately
• Final estimate is the sum of all parts
• Provides high accuracy in software estimation

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🔹 12. Quick Exam Answer (2–3 lines)

Decomposition techniques are software estimation methods in which a project is divided into smaller components, and each component is estimated separately. The total effort is obtained by combining all individual estimates, making it a more accurate approach.

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🔹 13. Likely Exam Questions

1. Define decomposition techniques.
2. Explain LOC-based estimation.
3. What is function point estimation?
4. List types of decomposition techniques.
5. Why is decomposition more accurate than top-down estimation?
6. Explain steps of decomposition estimation.
7. Draw diagram of decomposition process.