What’s the Functional Design Specification and A Demo

What’s the Functional Design Specification (FDS)

• Purpose: The FDS is a comprehensive description of the functionality that a software solution must offer. It details how the software should work and includes information about features, operations, and activities that the software must support.

• Audience: It is usually written for the development team but is also valuable for stakeholders, project managers, and testers to understand what is being built.

• Content: The FDS might include diagrams, data flow charts, screen layout designs, and other details that give a clear picture of functional aspects. It does not typically include the technical architecture or coding details.

• Role in Development: The FDS is used as a guide for developers and as a benchmark for testing and validation. It ensures that the final product aligns with the intended design and meets the user’s needs.

In software development, the creation of an FDS is an important step in the planning phase and is key to ensuring that all stakeholders have a common understanding of what the software will do. This document helps minimize the risk of misunderstandings or discrepancies between the expected and delivered functionalities.

A Sample: Functional Design Specification (FDS) for User Login and Logout Module

1. Introduction

This FDS document describes the functionality of the User Login and Logout Module for [Application Name]. The module will allow users to securely access their accounts and log out when their session is complete.

2. Scope

This module covers two primary functions:

1. User Login
2. User Logout

3. Functional Requirements

3.1 User Login

3.1.1 Input Fields

• Username/Email: The user must input a registered email address.
• Password: The user must input a password associated with the email.

3.1.2 Validation

• The system will validate the email format.
• Passwords must be at least 8 characters long.

3.1.3 Authentication Process

• The system will authenticate users against stored credentials in the database.
• If the credentials are incorrect, an error message “Invalid username or password” will be displayed.
• After three consecutive failed attempts, the account will be temporarily locked for 15 minutes.

3.1.4 Session Management

• Upon successful login, a session will be created.
• The session timeout is set to 30 minutes of inactivity.

3.1.5 Security

• Passwords will be encrypted in the database.
• The login page will be secured with HTTPS.

3.1.6 Redirect After Login

• Successful login will redirect the user to the dashboard/homepage.

3.2 User Logout

3.2.1 Logout Process

• Users can log out by clicking the ‘Logout’ button.
• The system will terminate the user’s session.

3.2.2 Redirect After Logout

• After logging out, users will be redirected to the login page.

3.2.3 Session Cleanup

• All session data will be cleared upon logout.

4. User Interface Design

4.1 Login Page

• A clean and responsive login page with input fields for email and password.
• A ‘Login’ button to submit credentials.
• Links for ‘Forgot Password’ and ‘Register New Account’.

4.2 Logout Functionality

• A clearly visible ‘Logout’ button on the top right corner of the user dashboard.

5. Error Handling

• Incorrect login details will trigger an error message.
• Account lock after multiple failed attempts will display a specific message.

6. Performance Requirements

• The login process should not take more than 5 seconds under normal server load conditions.

7. Accessibility

• The login form will be accessible and navigable using keyboard shortcuts and screen readers.

8. Testing Criteria

• Unit tests for the authentication process.
• System tests for session management and security.
• User acceptance testing for overall functionality and usability.