Software Development Essentials: SDLC, SRS, COCOMO, Agile & Risk

Posted on Apr 2, 2025 in Software Engineering

Functional vs. Non-Functional Requirements

Understanding the difference between functional and non-functional requirements is crucial in software development:

  • Functional Requirements: Specify what the system should do (features, actions, and behaviors).
  • Non-Functional Requirements: Define how the system should perform (quality attributes like performance, security).

Here’s a comparison:

  • Functional: Focuses on specific functionalities of the system.
  • Non-Functional: Focuses on system quality and constraints.
  • Functional: Examples include user login, data processing, and reporting.
  • Non-Functional: Examples include performance, scalability, and usability.
  • Functional: Can be easily measured based on system actions.
  • Non-Functional: Measured in terms of performance or quality (e.g., response time, uptime).
  • Functional: Changes directly affect how the system behaves.
  • Non-Functional: Changes typically affect system performance or user experience.
  • Functional: May involve specific time-related tasks (e.g., transaction completion).
  • Non-Functional: Often specifies constraints like response times, throughput.
  • Functional: Example test: Verify a user can successfully log in.
  • Non-Functional: Example test: Verify the system responds within 2 seconds.
  • Functional: Typically higher priority, as they define the core features of the system.
  • Non-Functional: Though important, usually considered secondary to functional requirements.
  • Functional: Directly linked to business operations or user goals.
  • Non-Functional: Affects the system’s efficiency, reliability, and user experience.

Software Development Lifecycle (SDLC)

The Software Development Lifecycle (SDLC) is a structured process used to design, develop, test, and maintain software. Here’s a brief overview of its key stages:

  1. Planning: Identifying the project scope, goals, resources, and timeline.
  2. Feasibility Study: Assessing the technical, operational, and financial feasibility of the project.
  3. Design: Creating system architecture and detailed design specifications, including user interfaces and data models.
  4. Development: Writing the actual code based on the design specifications.
  5. Testing: Verifying the software functions correctly and identifying bugs or issues.
  6. Deployment: Installing the software in a production environment for users to access.
  7. Maintenance: Ongoing updates, bug fixes, and improvements based on user feedback and system performance.

Software Requirements Specification (SRS)

SRS (Software Requirements Specification) is a document that provides a detailed description of a software system’s intended functionality, features, and behavior. It serves as a foundation for the software development process, ensuring that both developers and stakeholders have a clear understanding of the system requirements.

Components of SRS:

  1. Introduction:
    • Overview of the software, its purpose, and objectives.
    • Defines the intended audience and the scope of the system.
  2. Overall Description:
    • High-level description of the system’s context, user needs, and general system behavior.
  3. System Features:
    • Detailed description of the system’s functionalities and how they will operate.
  4. External Interface Requirements:
    • Specifies how the system will interact with external systems, hardware, and users (e.g., APIs, UI).
  5. System Attributes (Non-Functional Requirements):
    • Covers performance, security, scalability, reliability, and other quality attributes.
  6. Assumptions and Dependencies:
    • Lists assumptions and external dependencies that could affect system development or performance.
  7. Appendices:
    • Includes additional supportive material like glossaries, diagrams, or abbreviations.

COCOMO (Constructive Cost Model)

The COCOMO (Constructive Cost Model) is a software estimation model used to predict the effort, cost, and time required for a software development project. It helps project managers estimate resources needed based on the size of the project.

Key Points:

  1. Basic COCOMO Model:
    • It calculates the effort in person-months based on the size of the software (measured in thousands of lines of code or KLOC).
  2. Intermediate COCOMO Model:
    • It includes additional factors like product complexity, reliability, and team experience to refine the estimate.
  3. Detailed COCOMO Model:
    • Expands on the intermediate model by evaluating project phases (e.g., design, coding, testing) with different cost drivers to provide more accurate estimates.

COCOMO helps manage software projects by providing a systematic approach to estimating resources and timelines. It has been widely used for decades to improve project planning and budgeting.

Agile Software Development

Agile Software Development is important because it focuses on delivering high-quality software through iterative development, flexibility, and close collaboration between development teams and stakeholders. Here are the key reasons why Agile is important:

  1. Flexibility and Adaptability: Agile allows changes to be easily incorporated throughout the development process, enabling teams to respond to shifting requirements or market conditions.
  2. Faster Time to Market: Through iterative cycles (sprints), Agile delivers working software quickly and continuously, enabling faster release of features.
  3. Customer Collaboration: Agile emphasizes frequent communication with stakeholders and customers to ensure the product meets their needs and expectations.
  4. Improved Quality: Regular testing and feedback ensure that issues are identified and resolved early, resulting in higher-quality software.
  5. Enhanced Team Collaboration: Agile encourages teamwork, transparency, and regular meetings, fostering better communication and decision-making among all team members.
  6. Continuous Improvement: Agile promotes reflection at the end of each iteration to improve processes, tools, and performance.

Waterfall Model: Advantages and Disadvantages

Advantages of the Waterfall Model:

  1. Simplicity and Easy to Understand: The linear and sequential approach is straightforward and easy to follow.
  2. Clear Documentation: Each phase has well-defined documentation, making it easier to understand project requirements and design.
  3. Structured Approach: It provides a clear, systematic approach with milestones, which helps in managing large projects with well-defined goals.
  4. Easy to Manage: Since each phase is completed before moving to the next, it’s easier to track progress and maintain control over the project.

Disadvantages of the Waterfall Model:

  1. Inflexibility: Once a phase is completed, it’s difficult to go back and make changes, making it less adaptable to changing requirements.
  2. Late Testing: Testing only happens after development, which can lead to the late discovery of defects.
  3. Assumes Clear Requirements: The model assumes that requirements are fully understood upfront, which is often not the case in real-world projects.
  4. Not Ideal for Complex or Evolving Projects: The rigid structure doesn’t accommodate projects with evolving needs or complex requirements well.

Software Risk Management

Risk Management refers to the process of identifying, assessing, and prioritizing risks, followed by the application of resources to minimize, monitor, and control the probability or impact of unfortunate events or to maximize the realization of opportunities. In software development, it focuses on managing risks that could impact the project’s success.

Software Risk Management Process:

  1. Risk Identification:
    • Identifying potential risks that could affect the software project, such as technical challenges, resource limitations, schedule delays, or changing requirements.
  2. Risk Assessment:
    • Analyzing the identified risks in terms of their likelihood of occurrence and potential impact on the project. This helps prioritize which risks to address first.
  3. Risk Mitigation/Response Planning:
    • Developing strategies to manage or reduce the impact of risks. This could involve preventive actions, creating contingency plans, or making changes to the project approach.
  4. Risk Monitoring and Control:
    • Continuously tracking risks throughout the project lifecycle to ensure that they are being managed effectively. Adjust plans and responses as new risks emerge or existing risks evolve.
  5. Risk Review:
    • Periodically reviewing the risks and the effectiveness of the risk management process, ensuring that the strategies are still relevant and adjusting them as needed.