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Software Engineering - 2019



1. Describe the three-phase of the generic view of Software Engineering.

Software engineering follows a generic process model that consists of three primary phases:

(i) Definition Phase

  • This phase focuses on understanding what the system should do.
  • It involves gathering, analyzing, and specifying requirements.
  • Key activities include:
    • Requirement Analysis – Identifying the needs of users.
    • Feasibility Study – Checking if the project is practical and achievable.
    • System Specification – Documenting the software requirements.

(ii) Development Phase

  • This phase is focused on how the system will be built.
  • It includes designing, coding, and testing the software.
  • Key activities include:
    • Software Design – Creating architecture and detailed system design.
    • Coding – Writing the actual program using programming languages.
    • Testing – Checking for defects and verifying that the software works as expected.

(iii) Maintenance Phase

  • After deployment, software requires ongoing improvements and fixes.
  • Key activities include:
    • Bug Fixing – Resolving errors and issues reported by users.
    • Enhancements – Adding new features as per customer needs.
    • Performance Optimization – Improving speed, efficiency, and security.

2. What are the differences between Waterfall and Prototype models?

Feature Waterfall Model Prototype Model
Definition A linear, sequential approach to software development. An iterative approach where a prototype is built before the final system.
Phases Requirements → Design → Implementation → Testing → Deployment → Maintenance. A working prototype is created, tested, and improved based on user feedback before the final development.
Flexibility Rigid and less flexible, as changes are difficult to accommodate. More flexible, allowing changes and improvements at an early stage.
User Involvement Users provide input only during the requirements phase. Users provide continuous feedback during development.
Cost & Time Cheaper initially but costly if changes are needed later. Can be more expensive due to multiple iterations, but reduces risks.
Best Used For Well-defined projects with clear requirements. Projects where requirements are unclear or evolving.

3. List various objectives of Software Project Planning.

Software project planning is essential to ensure a structured and efficient development process. Key objectives include:

  1. Define Scope & Objectives – Clearly specify what the project aims to achieve.
  2. Estimate Time & Cost – Predict how long the project will take and how much it will cost.
  3. Resource Allocation – Assign human, technical, and financial resources efficiently.
  4. Risk Management – Identify potential risks and create strategies to mitigate them.
  5. Quality Assurance – Ensure the software meets the required standards.
  6. Project Scheduling – Develop a timeline with milestones and deadlines.
  7. Stakeholder Communication – Keep clients and team members informed about progress.
  8. Change Management – Plan how to handle modifications in requirements.

4. What is a Software Process?

A Software Process refers to a structured set of activities involved in developing software. It defines how software is:

  • Developed – From planning to coding and testing.
  • Managed – Ensuring quality, cost, and timely delivery.
  • Maintained – Updating and fixing software after deployment.

Key Stages of a Software Process:

  1. Requirement Analysis – Gathering user needs.
  2. System Design – Creating blueprints and architecture.
  3. Implementation – Writing the actual code.
  4. Testing – Checking for bugs and errors.
  5. Deployment – Releasing the software for use.
  6. Maintenance – Providing updates and fixing issues.

Types of Software Processes:

  • Waterfall Model (Sequential approach)
  • Agile Model (Iterative approach)
  • Spiral Model (Risk-driven approach)
  • V-Model (Validation and verification model)

5. Briefly describe Forward Engineering.

Forward Engineering is the process of developing a system from high-level specifications or design documents into an actual implementation.

Key Features of Forward Engineering:

  • Starts from analysis and moves forward to coding and testing.
  • Uses well-defined models and documentation.
  • Leads to the creation of fully functional software.

Steps in Forward Engineering:

  1. Requirement Gathering – Understand user needs.
  2. System Design – Create architecture and design models.
  3. Implementation – Develop software using programming languages.
  4. Testing – Ensure software meets requirements.
  5. Deployment & Maintenance – Release software and provide updates.

Example of Forward Engineering:

  • Converting a UML (Unified Modeling Language) design into Java or Python code.

Section-B: Short Answer Type Questions

6. Describe various Decomposition Techniques. Explain COCOMO Model with an example.

Decomposition Techniques in Software Engineering

Decomposition techniques are used to break down complex software problems into smaller, manageable parts. The primary decomposition methods include:

  1. Functional Decomposition: The system is divided into functions or modules, each handling a specific operation.
  2. Object-Oriented Decomposition: The system is divided into objects that encapsulate both data and behavior.
  3. Process-Oriented Decomposition: The system is broken into processes, each responsible for a specific task.
  4. Feature-Oriented Decomposition: Divides the system based on features or functionalities.
  5. Data-Oriented Decomposition: Breaks the system into data structures and their relationships.

COCOMO (Constructive Cost Model)

COCOMO is a widely used software cost estimation model proposed by Barry Boehm. It helps estimate project cost, effort, and time based on the project size (Lines of Code, LOC). It has three types:

  1. Basic COCOMO: Estimates based on the size of the software only.
  2. Intermediate COCOMO: Considers cost drivers like experience, technology, and constraints.
  3. Detailed COCOMO: Includes phase-wise effort estimation.
Example

For a simple project with 10,000 LOC in the Organic Mode, the effort is calculated as: Effort = 2.4 × (10)^1.05 = 25.1 person-months.

7. What are the various factors associated with cost estimation of a project? Explain cost estimation techniques in detail.

Factors Affecting Cost Estimation

Several factors influence the cost of software development:

  1. Project Size: Larger projects require more resources and time.
  2. Complexity: Higher complexity leads to increased effort and cost.
  3. Technology Used: Advanced technologies may require specialized skills, increasing cost.
  4. Development Team Skills: Experienced teams may reduce development time and cost.
  5. Hardware & Software Costs: Additional tools and infrastructure can raise costs.
  6. Risk Factors: Unexpected challenges or changes impact cost.

Cost Estimation Techniques

  1. Expert Judgment: Based on experience and knowledge of similar projects.
  2. Analogy-Based Estimation: Comparing with previously completed projects.
  3. COCOMO Model: Uses mathematical formulas to estimate cost.
  4. Function Point Analysis (FPA): Measures software size based on functions rather than LOC.
  5. Parametric Estimation: Uses statistical models to predict effort and cost.
  6. Bottom-Up Estimation: Estimates cost for individual components and sums them up.

8. Differentiate between the top-down and the bottom-up approach in designing software.

Feature Top-Down Approach Bottom-Up Approach
Definition Starts with the overall system and breaks it into smaller modules. Begins with designing small components and integrating them into a complete system.
Process Divides the problem into smaller sub-problems. Develops independent modules first, then combines them.
Design Focus Emphasizes system-wide design first. Focuses on developing independent reusable components.
Testing Approach Uses integration testing from top to bottom. Uses unit testing on individual components first.
Example Designing a car by defining the full structure first and then working on components like engine, wheels, etc. Designing a car by first developing and testing components like engine, seats, and dashboard separately, then assembling them.

Both approaches have their use cases. The top-down approach is suitable for systems with well-defined requirements, while the bottom-up approach is useful for modular development and code reusability.

Section-C: Detailed Answers

9. What is Agile Methodology? Discuss the principle of Agile Method.

Agile methodology is an iterative approach to software development that emphasizes flexibility, customer collaboration, and rapid delivery of functional software. Unlike traditional waterfall models, Agile allows for continuous feedback and adaptation, making it ideal for projects with changing requirements.

Principles of Agile Methodology:

  1. Customer Collaboration Over Contract Negotiation – Agile teams work closely with customers to ensure the product meets their needs.
  2. Individuals and Interactions Over Processes and Tools – Focus is on teamwork and communication rather than rigid tools and processes.
  3. Working Software Over Comprehensive Documentation – Delivering a functional product is prioritized over excessive documentation.
  4. Responding to Change Over Following a Plan – Agile allows for changes in requirements, even in later stages of development.
  5. Iterative Development – Work is divided into small iterations or sprints, each delivering a working feature.
  6. Continuous Feedback and Improvement – Regular feedback loops help refine the project.
  7. Simplicity and Efficiency – Agile teams aim to keep designs simple and improve them incrementally.

Agile Frameworks:

  • Scrum: Divides work into sprints of 2-4 weeks, with roles like Scrum Master, Product Owner, and Development Team.
  • Kanban: Focuses on continuous delivery and workflow visualization.
  • Extreme Programming (XP): Prioritizes high-quality coding standards and frequent releases.

Advantages of Agile:

  • Faster time to market
  • Increased flexibility and adaptability
  • Enhanced team collaboration and productivity
  • Higher customer satisfaction

10. Discuss Cyclomatic Complexity Used to Define the Complexity of Source Code.

Cyclomatic complexity is a software metric that quantifies the complexity of a program's control flow. It measures the number of independent paths through the source code, helping developers assess the maintainability and testability of software.

Calculation of Cyclomatic Complexity:

McCabe’s formula for cyclomatic complexity (V(G)) is:

V(G) = E - N + 2P Where:

  • E = Number of edges in the control flow graph
  • N = Number of nodes in the control flow graph
  • P = Number of connected components (usually 1 for a single program)

Example Calculation:

Consider a simple program with 3 decisions:

  • Number of edges (E) = 7
  • Number of nodes (N) = 5
  • V(G) = 7 - 5 + 2 = 4

Importance of Cyclomatic Complexity:

  • Helps in determining test cases.
  • Indicates potential areas of high risk and complexity.
  • Ensures better code maintainability.
  • Reduces chances of errors by keeping complexity low.

Recommended complexity values:

  • 1-10: Simple program (easily testable and maintainable)
  • 11-20: Moderate complexity (requires attention)
  • 21-50: High complexity (needs refactoring)

  • 50: Very complex (should be restructured)

11. What is Software Design? Explain It with the Help of Principles and Concepts.

Software design is the process of defining the architecture, components, interfaces, and data of a system to satisfy specified requirements. It acts as a blueprint for both development and maintenance.

Principles of Software Design:

  1. Modularity – Breaking software into smaller, manageable modules.
  2. Abstraction – Hiding complex implementation details.
  3. Encapsulation – Restricting direct access to some components.
  4. Separation of Concerns – Dividing software into distinct sections.
  5. Low Coupling and High Cohesion – Ensuring modules are independent yet well-connected.
  6. Scalability and Maintainability – Designing for future growth and ease of modification.

Concepts of Software Design:

  • Architectural Design: High-level structure defining major components.
  • Detailed Design: Low-level design of individual components and interactions.
  • Design Patterns: Reusable solutions to common design problems (e.g., Singleton, Factory, Observer).

A well-structured design ensures efficiency, scalability, and maintainability of software applications.

12. How is the Cost of Software Estimated? Discuss in Detail.

Software cost estimation is the process of predicting the effort, time, and resources required to develop a software project. It plays a crucial role in project planning, budgeting, and resource allocation. Accurate cost estimation helps in avoiding budget overruns and ensures project success.

Cost Estimation Techniques:

  1. Expert Judgment – Based on past experience and domain knowledge, experts provide an estimated cost.
  2. Algorithmic Models – Mathematical formulas are used to calculate costs based on project size and complexity. Example: COCOMO (Constructive Cost Model).
  3. Empirical Models – Uses historical data from previous projects to predict costs.
  4. Analogy-Based Estimation – Compares the project with similar past projects to estimate effort and cost.
  5. Bottom-Up Estimation – Breaks down the project into smaller components and estimates cost for each component individually.
  6. Top-Down Estimation – Provides a rough estimate based on high-level project specifications.

Cost Estimation Models:

  • COCOMO (Constructive Cost Model):
    • Basic: Estimates cost based on lines of code (LOC).
    • Intermediate: Considers additional factors like team capability and complexity.
    • Detailed: Provides highly accurate estimation using multiple parameters.
  • Function Point Analysis (FPA):
    • Estimates cost based on user inputs, outputs, files, and external interfaces.
  • Use Case Points (UCP):
    • Determines cost based on the number and complexity of use cases in the system.

Factors Affecting Cost Estimation:

  • Project Complexity – More complex projects require more effort and resources.
  • Team Experience and Skills – Experienced teams can complete tasks more efficiently, reducing cost.
  • Development Methodology – Agile projects may have different cost structures than Waterfall projects.
  • Software Requirements and Scope – Larger scope leads to higher costs.
  • Technology Stack – The choice of programming languages, frameworks, and tools affects cost.
  • Testing and Maintenance Costs – Post-development maintenance also contributes to total cost.

By applying these techniques, software development teams can create accurate budget plans and avoid financial risks.

13. What is the Role of Modularity? Explain the Role of Coupling and Cohesion in Software Design.

Role of Modularity:

Modularity is a fundamental design principle that divides a software system into smaller, manageable, and independent modules. Each module is responsible for a specific functionality, making the software easier to develop, maintain, and scale.

Advantages of Modularity:

  1. Enhanced Reusability – Modules can be reused in different projects, reducing redundancy.
  2. Easier Debugging and Testing – Isolated modules allow for independent testing.
  3. Improved Maintainability – Changes can be made to a module without affecting others.
  4. Faster Development – Different teams can work on separate modules simultaneously.
  5. Scalability – New features can be added without disrupting the entire system.

Role of Coupling and Cohesion in Software Design:

Coupling:

Coupling refers to the degree of dependency between modules. Lower coupling is desirable as it makes the system more modular and flexible.

Types of Coupling:

  • High Coupling (Bad):
    • Modules are highly dependent on each other.
    • Changes in one module affect others, making maintenance difficult.
  • Low Coupling (Good):
    • Modules have minimal dependencies.
    • Enhances modularity, making the system more flexible and maintainable.

Cohesion:

Cohesion refers to how well the internal elements of a module work together. High cohesion is desirable as it ensures that a module is focused on a single task.

Types of Cohesion:

  • Low Cohesion (Bad):
    • Module performs multiple unrelated tasks.
    • Leads to increased complexity and reduced reusability.
  • High Cohesion (Good):
    • Module is focused on a single responsibility.
    • Enhances maintainability, readability, and reusability.

Importance of Balancing Coupling and Cohesion:

  • High cohesion and low coupling lead to well-structured, maintainable software.
  • Highly coupled systems are harder to test, modify, and debug.
  • Poor cohesion results in inefficient modules that lack clarity and purpose.


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