Non-Functional Requirements Analysis

Non-Functional Requirements Analysis: A Complete Guide for CBAP Exam

Introduction to Non-Functional Requirements Analysis

Non-Functional Requirements Analysis is a critical component of the Requirements Analysis and Design Definition knowledge area in the Certified Business Analyst Professional (CBAP) certification. This guide provides a comprehensive understanding of this essential business analysis discipline.

Why Non-Functional Requirements Analysis is Important

Non-functional requirements (NFRs) are crucial because they define how well a system should perform rather than what it should do. Understanding their importance includes:

• System Quality: NFRs ensure the system meets quality standards such as reliability, maintainability, and usability
• User Satisfaction: Performance, security, and usability requirements directly impact user experience and satisfaction
• Business Value: NFRs like scalability and availability directly support business continuity and growth
• Risk Mitigation: Identifying NFRs early prevents costly redesigns and system failures
• Cost Management: Clear NFRs help estimate resources, timelines, and budgets more accurately
• Legal Compliance: Security, privacy, and regulatory requirements ensure organizational compliance
• Competitive Advantage: Superior performance, reliability, and user experience differentiate solutions in the market

What Non-Functional Requirements Are

Definition: Non-functional requirements are constraints, qualities, or characteristics that a system must possess to be considered acceptable. They describe how well the system should perform its functions, not what functions it performs.

Key Characteristics of NFRs:

• Focus on system properties and quality attributes rather than specific functions
• Apply across multiple functional requirements
• Often difficult to test and measure objectively
• Become more critical as systems scale and become more complex
• Require careful prioritization and trade-off analysis

Common Categories of Non-Functional Requirements:

• Performance: Response time, throughput, latency, and speed of operations
• Scalability: Ability to handle increased load and data volumes
• Reliability: System uptime, fault tolerance, and mean time between failures (MTBF)
• Availability: Percentage of time the system is operational and accessible
• Security: Authentication, authorization, encryption, and data protection mechanisms
• Usability: User interface intuitiveness, accessibility, and user experience quality
• Maintainability: Ease of updating, fixing, and modifying the system
• Portability: Ability to run on different platforms, devices, or operating systems
• Compliance: Adherence to regulatory, legal, and industry standards
• Compatibility: Integration with existing systems and technologies
• Recoverability: Ability to restore system functionality after failures
• Supportability: Ease of providing customer support and technical assistance

How Non-Functional Requirements Analysis Works

Step 1: Identify Stakeholders and Their NFR Concerns

• Engage customers, users, operations teams, security officers, and system administrators
• Understand each stakeholder group's priorities and constraints
• Recognize that different stakeholders may have conflicting NFR expectations

Step 2: Elicit NFRs from Stakeholders

• Use interviews and focus groups to understand performance expectations
• Conduct workshops to discuss quality attributes and system behavior
• Review business strategies and organizational goals
• Analyze existing systems and their performance limitations
• Review industry benchmarks and competitor solutions
• Examine regulatory and compliance requirements

Step 3: Categorize and Organize NFRs

• Group requirements by category (performance, security, usability, etc.)
• Use templates or frameworks to ensure comprehensive coverage
• Document each NFR with clear descriptions and context
• Identify interdependencies between NFRs and functional requirements

Step 4: Define Measurable Criteria

• Convert qualitative NFRs into quantifiable metrics (e.g., "fast response" becomes "response time < 2 seconds")
• Establish baselines and targets for each metric
• Define acceptable thresholds and tolerance ranges
• Ensure criteria are verifiable and testable

Step 5: Analyze Trade-offs and Priorities

• Identify competing NFRs that create trade-offs (e.g., security vs. usability)
• Facilitate stakeholder discussions to establish priorities
• Document rationale for priority decisions
• Consider cost-benefit implications of each NFR
• Balance technical constraints with business needs

Step 6: Document and Communicate NFRs

• Create clear, unambiguous requirement statements
• Use tables, matrices, and diagrams to organize and present NFRs
• Include acceptance criteria and verification methods
• Ensure all stakeholders understand and agree on NFRs
• Maintain traceability to business objectives

Step 7: Validate and Verify NFRs

• Review requirements with stakeholders for completeness and accuracy
• Ensure NFRs are testable and measurable
• Validate that NFRs align with business goals and constraints
• Identify and resolve conflicts and ambiguities
• Obtain formal sign-off from key stakeholders

Step 8: Monitor and Control NFRs Throughout the Project

• Track changes to NFRs and assess their impact
• Monitor design and implementation decisions against NFR criteria
• Conduct performance testing and validation
• Address any gaps between planned and actual performance
• Document lessons learned for future projects

Key Techniques for Non-Functional Requirements Analysis

Quality Function Deployment (QFD): Maps customer needs to technical requirements, helping prioritize NFRs based on customer value

Performance Testing: Simulates real-world conditions to validate that NFRs can be achieved

Benchmarking: Compares proposed NFRs against industry standards and competitor products

Prototyping: Creates early prototypes to test usability and performance characteristics

Requirements Matrices: Documents and organizes NFRs with attributes such as priority, rationale, and verification method

SMART Criteria: Ensures NFRs are Specific, Measurable, Achievable, Relevant, and Time-bound

Failure Mode Analysis: Identifies potential system failures and reliability requirements needed to prevent them

Common Challenges in Non-Functional Requirements Analysis

• Ambiguity: NFRs are often vague and subjective; converting them to measurable metrics is difficult
• Stakeholder Disagreement: Different stakeholders prioritize different NFRs, leading to conflicts
• Hidden Requirements: Stakeholders may not explicitly state some important NFRs
• Technical Feasibility: Some desired NFRs may be technically impossible or prohibitively expensive
• Evolution Over Time: NFRs change as technology and business needs evolve
• Testing Difficulty: Some NFRs are harder to test than functional requirements
• Trade-off Complexity: Improving one NFR may negatively impact another

How to Answer Exam Questions on Non-Functional Requirements Analysis

Question Type 1: Definition and Identification Questions

These ask you to identify or define non-functional requirements.

• Strategy: Remember that NFRs describe qualities and how well functions are performed, not what functions are performed
• Key Point: Look for words like "performance," "reliability," "security," "usability," and "scalability"
• Example Answer Structure: "Non-functional requirements define system qualities such as performance, security, and reliability that constrain how functional requirements are implemented."

Question Type 2: Categorization Questions

These ask you to categorize requirements as functional or non-functional, or to classify NFRs into specific types.

• Strategy: Ask yourself: "Does this requirement describe what the system should do (functional) or how well it should do it (non-functional)?"
• Key Point: Distinguish between performance (NFR) and a calculation or process (Functional)
• Example: "The system shall process 1,000 transactions per minute" is an NFR (performance), while "The system shall calculate monthly invoices" is a functional requirement

Question Type 3: Analysis and Trade-off Questions

These present scenarios with competing or conflicting NFRs and ask how to handle them.

• Strategy: Identify the competing requirements, explain the trade-off, and describe how to resolve it through stakeholder engagement and prioritization
• Key Point: Emphasize communication, documentation of rationale, and sign-off from key stakeholders
• Example Answer Structure: "Security and usability often conflict. A business analyst should facilitate a discussion with stakeholders, document the trade-off rationale, and help select a balanced approach that meets business priorities."

Question Type 4: Elicitation and Documentation Questions

These ask how to gather or document NFRs.

• Strategy: Describe techniques such as interviews, workshops, benchmarking, and performance testing
• Key Point: Emphasize the importance of making NFRs measurable and testable
• Example Answer Structure: "Conduct stakeholder interviews and workshops to understand performance expectations, review industry benchmarks, and document each NFR with specific, measurable criteria such as response time < 2 seconds."

Question Type 5: Validation and Verification Questions

These ask how to verify that NFRs have been met.

• Strategy: Discuss testing approaches, acceptance criteria, and stakeholder review
• Key Point: Connect testing to specific, measurable criteria established during analysis
• Example Answer Structure: "Validate NFRs through performance testing under realistic load conditions, compare results against established criteria, and obtain stakeholder sign-off."

Exam Tips: Answering Questions on Non-Functional Requirements Analysis

Tip 1: Understand the Distinction Between Functional and Non-Functional Requirements

This is the most fundamental concept. Functional requirements describe what the system does (features and functions). Non-functional requirements describe how well it does it (qualities, performance, reliability). Practice identifying each type until it becomes second nature.

Tip 2: Know the Major Categories of NFRs

Be familiar with the major NFR categories: performance, scalability, reliability, availability, security, usability, maintainability, portability, compliance, compatibility, recoverability, and supportability. When you encounter a scenario, classify the NFR into one of these categories. This demonstrates clear understanding to the exam.

Tip 3: Always Connect NFRs to Business Value

In your answers, explain why an NFR matters to the business. For example, don't just say "security is important"—explain that "security is critical because it protects customer data, ensures regulatory compliance, and builds customer trust." The CBAP values business-oriented analysis.

Tip 4: Emphasize Measurability and Testability

When discussing NFRs, always mention converting vague requirements into measurable criteria. Use phrases like "specific metrics," "quantifiable thresholds," and "acceptance criteria." Examiners want to see that you understand NFRs must be testable.

Tip 5: Discuss Trade-offs and Stakeholder Management

Many exam questions present scenarios with competing or conflicting NFRs. Your answer should always include stakeholder engagement, discussion of trade-offs, and documented decision-making. Show that you understand balancing competing interests is a key BA skill.

Tip 6: Use a Structured Approach to Analysis

When answering questions about how to analyze NFRs, use a logical, step-by-step approach: identify stakeholders → elicit requirements → categorize → define metrics → analyze trade-offs → document → validate. This demonstrates mature analysis practices.

Tip 7: Know How to Handle Common Challenges

Be prepared to discuss how to address ambiguity in NFRs, hidden or unstated requirements, conflicting stakeholder priorities, and technical feasibility constraints. Show problem-solving skills by proposing solutions like workshops, prototyping, or benchmarking.

Tip 8: Connect NFRs to Design and Implementation

Understand that NFRs influence design and architecture decisions. For example, high-availability requirements drive decisions about redundancy and failover mechanisms. High-security requirements influence authentication and encryption design. Show this connection in your answers.

Tip 9: Remember Requirements Traceability

Discuss maintaining traceability from NFRs through design, implementation, testing, and deployment. This shows understanding of the complete requirements lifecycle and how analysis work flows into project execution.

Tip 10: Use Real-World Context in Your Answers

When possible, reference realistic scenarios (e.g., "An e-commerce system has a peak load of 10,000 concurrent users, so scalability is critical"). This shows practical understanding beyond theoretical knowledge and is highly valued in professional certifications.

Tip 11: Don't Forget About Constraints and Feasibility

In your answers, acknowledge that not all desired NFRs are technically feasible or cost-effective. Show that a mature business analyst balances ideal requirements with practical constraints and helps stakeholders make informed priority decisions.

Tip 12: Practice with Scenario-Based Questions

The CBAP exam heavily features scenario-based questions. Practice identifying NFRs in complex, real-world scenarios. Learn to distinguish NFRs from functional requirements in messy, ambiguous situations—this is where true competency is demonstrated.

Key Terminology to Master

• Quality Attributes: The non-functional properties that define system excellence
• Performance Metrics: Measurable indicators of system performance (response time, throughput, latency)
• Service Level Agreement (SLA): Documented NFR targets and acceptable performance ranges
• Scalability: The system's ability to handle increasing load and data volume
• Reliability: The probability that the system will function without failure over a specified period
• Availability: The percentage of time the system is operational and accessible
• Acceptance Criteria: Specific, testable conditions that NFRs must satisfy
• Trade-off Analysis: The process of evaluating competing NFRs and making priority decisions
• Requirements Traceability: The ability to track NFRs from analysis through design, implementation, and testing
• Verification: Confirming that the system was built correctly according to design specifications
• Validation: Confirming that the correct system was built to meet business needs and NFRs

Conclusion

Non-Functional Requirements Analysis is a sophisticated discipline that separates competent business analysts from excellent ones. By mastering the concepts, techniques, and approaches outlined in this guide, you'll be well-prepared to answer CBAP exam questions on this critical topic. Remember to focus on measurability, stakeholder engagement, trade-off management, and clear documentation. These skills not only help you pass the exam but also prepare you for real-world success as a certified business analyst.