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List and explain various types of requirements with example.

Software requirements can be classified into several categories based on their nature, purpose, and level of detail. Here are the main types of requirements:

1. Functional Requirements​

Functional requirements describe what the system should do, specifying the functions or services that the system must provide.

Examples:

  • A banking system shall allow users to withdraw money from their accounts
  • An e-commerce platform shall calculate tax based on the customer's location
  • A text editor shall allow users to save documents in multiple formats
  • A user authentication system shall lock an account after three failed login attempts

2. Non-Functional Requirements​

Non-functional requirements specify criteria that judge the operation of a system, rather than specific behaviors. They define quality attributes, constraints, or performance characteristics.

a) Performance Requirements​

  • The system shall load search results within 2 seconds for 90% of searches
  • The application shall support 10,000 concurrent users without performance degradation
  • Database queries shall complete within 500 milliseconds

b) Security Requirements​

  • User passwords shall be stored using SHA-256 hashing with salt
  • All data transmissions shall be encrypted using TLS 1.3
  • The system shall enforce role-based access control for all administrative functions

c) Usability Requirements​

  • The user interface shall be navigable using keyboard shortcuts for all major functions
  • Error messages shall be comprehensible to non-technical users
  • The application shall be usable by individuals with color blindness

d) Reliability Requirements​

  • The system shall have 99.9% uptime (no more than 8.76 hours of downtime per year)
  • The system shall automatically recover from database connection failures
  • No single point of failure shall exist in the system architecture

e) Scalability Requirements​

  • The database shall handle up to 1 million records without performance degradation
  • The system architecture shall allow adding server instances without downtime
  • Storage capacity shall be expandable to 10TB

3. Domain Requirements​

Domain requirements come from the application domain and reflect characteristics of that domain or constraints within it.

Examples:

  • A healthcare system shall comply with HIPAA regulations for patient data privacy
  • A financial application shall implement double-entry bookkeeping principles
  • An air traffic control system shall use standard aviation terminology and protocols

4. User Requirements​

User requirements describe user goals or tasks that users must be able to perform with the system.

Examples:

  • Marketing managers shall be able to generate sales reports by region, product, and time period
  • Customers shall be able to track the status of their orders in real-time
  • Teachers shall be able to assign homework and grade submissions through the platform

5. System Requirements​

System requirements are detailed descriptions of the system's functions, services, and operational constraints.

Examples:

  • The system shall use OAuth 2.0 for third-party authentication services
  • The mobile application shall operate offline and synchronize data when connectivity is restored
  • The system shall maintain an audit log of all administrative actions

6. Business Requirements​

Business requirements describe high-level needs of the organization or customer requesting the system.

Examples:

  • The new CRM system shall reduce customer service response time by 15%
  • The inventory management system shall decrease stockout incidents by 25%
  • The automated billing system shall reduce invoicing errors by 90%

7. Interface Requirements​

Interface requirements specify how the system interacts with users, hardware, and other software.

Examples:

  • The system shall provide a REST API for third-party integrations
  • The payment processing module shall interface with PayPal, Stripe, and Square
  • The mobile application shall support Android 10+ and iOS 13+

8. Transition Requirements​

Transition requirements describe what is needed to transition from the existing system or process to the new system.

Examples:

  • The system shall import all customer data from the legacy database
  • User training shall be provided through in-app tutorials and help documentation
  • The system rollout shall occur in phases by department, starting with Accounting

Properly identifying and categorizing requirements helps ensure that all aspects of the system are considered during development, leading to a more complete and successful solution that meets stakeholder needs.