By continuing to browse this website, you agree to our use of cookies. Learn more at the Privacy Policy page.
Contact Us
Contact Us
Functional vs. Non-functional requirements

What are software requirements?

Software requirements define what a system should do (functional) and how it should perform (non-functional). These requirements serve as the foundation for system design, development, and testing, ensuring that the final product meets business needs and user expectations while maintaining quality, performance, and reliability standards.

Key characteristics of well-defined requirements:

  • Clear, unambiguous, and testable specifications
  • Alignment with business objectives
  • Stakeholder consensus and validation
  • Traceability throughout the development lifecycle
  • Integration with cross-functional alignment processes
  • Support for real-time system behaviors
  • Consideration of tool ecosystem constraints

Functional Requirements

Definition

Functional requirements specify what the system should do – the functions, features, and capabilities that the system must provide to meet business and user needs. These are typically expressed as:

  • “The system shall…” statements
  • Use cases and user stories
  • Feature specifications
  • Business process automations
  • Data processing requirements
  • Integration points with other systems
  • API specifications for vendor integrations

Types of Functional Requirements

Business Requirements

High-level needs:

  • Business process automations
  • Reporting and analytics capabilities
  • Workflows and approval processes
  • Compliance and regulatory features
  • Integration with enterprise systems
  • Support for context-aware business processes

User Requirements

User-facing features:

  • User interface elements
  • User interactions and experiences
  • Accessibility features
  • Personalization capabilities
  • Notification and alert systems
  • Integration with event-driven user experiences

System Requirements

Technical functionalities:

  • Data processing capabilities
  • Algorithm implementations
  • System interfaces
  • Error handling and recovery
  • Batch and real-time processing requirements
  • Integration with external systems

Data Requirements

Information management:

  • Data collection and storage
  • Data transformation and enrichment
  • Data validation rules
  • Data retention policies
  • Integration with data pipelines
  • Handling of data migration scenarios

Non-Functional Requirements

Definition

Non-functional requirements specify how the system should perform its functions – the quality attributes, constraints, and performance characteristics that determine how well the system meets user expectations. These are often expressed as:

  • “The system shall be…” statements
  • Quality attribute scenarios
  • Performance metrics
  • Security and compliance standards
  • Operational constraints
  • Architectural qualities
  • Integration with cloud platform requirements

Categories of Non-Functional Requirements

Performance Requirements

System efficiency metrics:

  • Response time (e.g., <200ms for API calls)
  • Throughput (e.g., 10,000 requests/second)
  • Resource utilization (CPU, memory, disk)
  • Scalability (horizontal/vertical)
  • Benchmark performance against data warehouse standards
  • Real-time processing requirements per best practices

Security Requirements

Protection standards:

  • Authentication and authorization
  • Data encryption (at rest and in transit)
  • Access control policies
  • Audit logging and monitoring
  • Compliance with regulations (GDPR, HIPAA, etc.)
  • Integration with content security standards
  • Vulnerability management

Reliability Requirements

System dependability:

  • Availability (e.g., 99.99% uptime)
  • Mean Time Between Failures (MTBF)
  • Mean Time To Repair (MTTR)
  • Fault tolerance and redundancy
  • Disaster recovery capabilities
  • Backup and restore procedures
  • Integration with event-driven recovery systems

Usability Requirements

User experience qualities:

  • User interface standards
  • Accessibility compliance (WCAG)
  • Learnability and intuitiveness
  • Error prevention and recovery
  • Consistency across platforms
  • Localization and internationalization
  • Integration with context-aware UX

Maintainability Requirements

Long-term system qualities:

  • Code quality standards
  • Documentation requirements
  • Modularity and componentization
  • Testability and test coverage
  • Deployment flexibility
  • Version compatibility
  • Integration with vendor maintenance standards

Operational Requirements

Deployment and management:

Functional vs. Non-Functional Requirements Comparison

AspectFunctional RequirementsNon-Functional Requirements
DefinitionWhat the system should doHow the system should do it
FocusFeatures and capabilitiesQuality attributes and constraints
Expression"System shall do X""System shall be Y"
Testing ApproachFunctional testingPerformance, security, usability testing
StakeholdersBusiness analysts, product ownersArchitects, QA engineers, DevOps
Impact of ChangeAffects specific featuresAffects the entire system architecture
DocumentationUse cases, user storiesQuality attribute scenarios, SLAs
Integration with AIFunctional capabilities of AI agentsPerformance and reliability of real-time AI systems
Cloud ConsiderationsFunctional capabilities on cloud platformsPerformance and security on cloud infrastructure

Requirements Engineering Process

Elicitation

Gathering techniques:

Analysis

Refinement approaches:

  • Requirements prioritization
  • Conflict resolution
  • Feasibility analysis
  • Risk assessment
  • Cost-benefit analysis
  • Alignment with data pipeline capabilities
  • Validation against real-time system constraints

Specification

Documentation standards:

Validation

Quality assurance methods:

  • Requirements reviews
  • Prototyping and user testing
  • Traceability matrix
  • Consistency checking
  • Feasibility validation
  • Integration with vendor requirement standards
  • Testing against real-time constraints

Challenges in Requirements Management

Ambiguity and Incompleteness

Common issues:

Changing Requirements

Management challenges:

Stakeholder Conflicts

Resolution approaches:

  • Competing business priorities
  • Technical vs. business tradeoffs
  • Budget constraints
  • Timeline disagreements
  • Quality vs. speed tradeoffs
  • Alignment with cross-functional priorities
  • Balancing real-time needs with other requirements

Technical Constraints

Implementation challenges:

  • Legacy system limitations
  • Performance bottlenecks
  • Security restrictions
  • Vendor dependencies per best practices
  • Data volume constraints
  • Integration complexities with cloud platforms
  • Real-time processing requirements

Best Practices for Requirements Management

Clear Documentation

Standards and techniques:

  • Use of standardized templates
  • Unambiguous language
  • Visual models and diagrams
  • Traceability matrices
  • Version control
  • Integration with documentation pipelines
  • Alignment with content standards

Prioritization Framework

Decision-making approaches:

  • MoSCoW method (Must, Should, Could, Won’t)
  • Kano model for customer satisfaction
  • Value vs. effort analysis
  • Risk-based prioritization
  • Business value assessment
  • Alignment with strategic objectives
  • Consideration of real-time priorities

Validation Techniques

Quality assurance methods:

Change Management

Adaptation strategies:

  • Version control systems
  • Impact analysis
  • Change control boards
  • Communication plans
  • Stakeholder notification
  • Integration with vendor change processes
  • Alignment with real-time update requirements

Emerging Trends in Requirements Engineering

Current developments:

  • AI-Augmented Requirements: Natural language processing for requirements analysis
  • Context-Aware Requirements: Using MCP protocols for complete context
  • Event-Driven Requirements: Integration with real-time systems
  • Agile and DevOps Integration: Continuous requirements refinement
  • Model-Based Systems Engineering: Visual requirement modeling
  • Requirements as Code: Version-controlled requirement specifications
  • Automated Validation: AI-powered requirements testing
  • Cloud-Native Requirements: Alignment with cloud platform capabilities
  • Data-Driven Requirements: Integration with analytics pipelines
Back to AI and Data Glossary

Let’s discuss your challenge

Schedule a call instantly here or fill out the form below

    photo 5470114595394940638 y