Requirements Engineering Overview

Requirements Engineering

• Requirements engineering is a critical step in software development.
• It involves creating and documenting requirements.
• Activities include elicitation, specification, analysis, verification, validation, and management.
• The process ensures the system benefits the organization, reflects client desires, and is in a standardized format.

Classifications of Software Requirements

• System requirements are statements of what a system must do to meet stakeholder needs.
• These needs are derived from business and user requirements.
• Requirements can be obvious, hidden, known, unknown, expected, or unexpected.
• Software requirements are categorized into three types: functional, non-functional, and domain.

Functional Requirements

• Define what the software should do.
• Describe functions or features.
• Example: User authentication—the system must allow users to log in using a username and password.
• Example: Search functionality—the software allows users to search for products by name or category.

Non-functional Requirements

• Describe how the software performs a task.
• Define quality attributes, performance criteria, and constraints.
• Examples:
  • Performance: The system should process 1,000 transactions per second.
  • Usability: The software should be easy to use and have a user-friendly interface.
  • Reliability: The system must have 99.9% uptime.
  • Security: Data must be encrypted during transmission and storage.

Domain Requirements

• Specific to the industry or domain.
• Include terminology, rules, and standards.
• Example: Healthcare—the software must comply with HIPAA regulations for handling patient data.

Other Requirement Classifications

• User requirements: Describe what end-users want from the system, expressed in natural language, usually through interviews, surveys, or user feedback.
• System requirements: Define technical characteristics like architecture, hardware, and interfaces, expressed in technical terms.
• Business requirements: Detail business goals and objectives for the software system.
• Regulatory requirements: Include legal or regulatory standards the software must meet, such as data privacy, security, and accessibility.
• Interface requirements: Specify interactions between the system and external components like databases, web services, or other software applications.
• Design requirements: Detail the software architecture, data structures, algorithms, and other technical aspects.

Software Requirements Specifications (SRS)

• The output of the requirements specification stage.
• It documents requirements clearly, concisely, and unambiguously.

Qualities of a good SRS

• Correctness: Includes all needed functionality.
• Completeness: Includes all essential requirements (functionality, performance, design, constraints, attributes, external interfaces) and definitions, input data categories, diagrams, and units of measure.
• Consistency: No conflicting requirements subsets.
• Unambiguousness: Each requirement should have a single meaning.
• Modifiability: The SRS should be adaptable to changes.
• Verifiability: SRS details allow verification of the final software.
• Traceability: Clear origin of requirements and linkage to other aspects.
• Design Independence: Options for various design alternatives.
• Testability: Requirements should be easily transformed into test cases.

Advantages of Classifying Requirements

• Better organization and management.
• Easier communication and collaboration.
• Improved quality due to early identification of conflicts.
• Effective traceability for demonstrating compliance.

Disadvantages of Classifying Requirements

• Complexity;
• Rigid structure limiting adaptability to change:
• Incorrect classifications leading to errors.

Requirements Engineering Process (RE)

• Identifies, elicits, analyzes, specifies, validates, and manages stakeholder needs.
• Crucial for project success;
• Stakeholder needs are met within budget, quality, and time.

Stages of Requirements Engineering

• Elicitation: Gathering requirements from various stakeholders.
• Analysis: Evaluating feasibility, consistency, and completeness of gathered requirements and resolutions of conflicts or contradictions.
• Modeling: Understanding system behavior by using diagrams.
• Specification: Documenting the requirements unambiguously and clearly.
• Validation: Ensuring accuracy, completeness, and consistency of the requirements.
• Management: Controlling changes and ensuring the requirements remain valid throughout the software development lifecycle.

Requirement Validation Techniques

• Test case generation: Creates tests to check requirements.
• Prototyping: Presents a working model to validate customer needs.
• Requirements reviews: Collective review by a group to identify errors and ambiguities.
• Automated consistency analysis: Automatically detects inconsistencies and errors.
• Simulation: Replicates real-world scenarios to verify requirements.
• Checklists for validation: Methodical verification of requirements.