Understanding Requirement Types: BABOK, Wiegers & Business Rules

Whether you're a Business Analyst (BA), Systems Analyst (SA), or an aspiring Product Manager, understanding requirement types is foundational to defining and delivering successful solutions.

But not all requirements are the same—and different frameworks categorize them differently. In this guide, you’ll learn:

• How requirements are classified in BABOK vs. Wiegers

• What each type of requirement actually represents

• Examples that bring each type to life

• Advanced types like transitional and non-functional requirements

First: What Is a Requirement?

A requirement is a defined need — it could be from the business, stakeholders, or technical side. Requirements describe what a solution must do or how it must behave to meet goals, solve problems, or satisfy users.

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BABOK Classification (by IIBA)

The BABOK Guide (v3) from the International Institute of Business Analysis (IIBA) defines four main types of requirements:

1. Business Requirements

High-level organizational goals or outcomes.
Example: “Increase market share by 10% within one year.”

2. Stakeholder Requirements

What stakeholders need to achieve the business goals.
Example: “As a Sales Manager, I want a dashboard to track regional performance.”

3. Solution Requirements

Detailed characteristics and capabilities of the solution. Split into:

• Functional Requirements – What the system must do.
  Example: “System must generate monthly sales reports.”

• Non-Functional Requirements (NFRs) – How well the system performs.
  Example: “The report must be generated in under 5 seconds.”

4. Transition Requirements

Temporary capabilities needed to move from the current state to the desired future state.
Example: “Train users on the new CRM before launch.”

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Wiegers’ Classification of Requirements

Karl Wiegers, a well-known software engineer and author, proposed a simpler, developer-friendly model often used in Agile and technical environments:

1. Business Requirements

Same as BABOK — the “why” behind the initiative.

2. User Requirements

Tasks or goals that users must be able to perform using the system.
Example: “Users should be able to reset their password.”

3. System Requirements

Detailed system specifications — both functional and non-functional.

• Functional: “System must validate login credentials.”

• Non-functional: “Support up to 10,000 concurrent users.”

Wiegers simplifies BABOK’s structure by merging stakeholder + solution requirements into user and system categories.

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Non-Functional Requirements (NFRs) & Business Rules

Non-Functional Requirements (NFRs)

These define how well the system performs rather than what it does.

Common NFRs include:

Type	Example
Performance	“System should respond within 1 second.”
Security	“Only managers can view payroll data.”
Usability	“Must be WCAG 2.1 accessible.”
Scalability	“Support doubling user load without delay.”
Availability	“Ensure 99.9% uptime.”

Business Rules

These are constraints, calculations, or policies the business must follow. They are not requirements themselves, but they influence or drive requirements.
Example: “Users must be 18+ to register.”

Transitional Requirements

These are temporary needs that support the rollout or implementation of the solution — but are not part of the final product.

Examples:

• Migrating data from the old system

• Temporary integrations

• Staff training or user onboarding programs

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Examples by Category

Requirement Type	Example
Business Requirement	“Expand into the European market in 2025.”
Stakeholder Requirement	“Sales reps must create quotes via tablet.”
Functional Requirement	“System must generate PDF invoices.”
Non-Functional Requirement	“Ensure 99.9% system uptime.”
User Requirement (Wiegers)	“Customer can track orders online.”
System Requirement (Wiegers)	“Use OAuth 2.0 for authentication.”
Transition Requirement	“Migrate customer data from legacy ERP.”
Business Rule	“Only verified users can submit complaints.”

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BABOK vs. Wiegers: Which Should You Use?

Aspect	BABOK	Wiegers
Best For	Business Analysts	Systems Analysts, Technical BAs
Structure	4 Types (Business, Stakeholder, Solution, Transition)	3 Types (Business, User, System)
Highlights	Includes stakeholder + transition	Simpler, developer-friendly
Commonly Used In	IIBA environments, enterprise projects	Agile teams, technical environments

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Pro Tip: Learn Both

• Use BABOK to structure requirements when working with stakeholders, business teams, and formal documentation.

• Use Wiegers when collaborating with developers and Agile teams.

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Final Thoughts

Understanding the types of requirements isn't just a theoretical exercise—it's a practical skill that strengthens everything you do:

• Writing user stories

• Running workshops

• Defining system behavior

• Communicating between business and technical teams

Mastering how to identify, organize, and explain different requirement types sets you apart as a high-impact BA, SA, or PM-in-the-making.