Requirements Engineering: 9 Best Practices with Examples

If you work in a regulated industry like medical device design, automotive engineering, or aerospace, you understand that requirements are the bedrock of product development. Without clear, effective requirements, your team risks compliance failures, scope creep, and costly rework.  

Requirements engineering is the disciplined application of proven principles, methods, and tools to describe the behavior of a proposed system. It is more than just writing down what a stakeholder wants; it is about ensuring those needs are verifiable, actionable, and traceable throughout the entire development lifecycle.

This guide explains how to write requirements by outlining nine best practices. It includes examples and a checklist to help you refine your own process.

1. Know Your Audience and Tailor Information

Before you type a single word, understand who will read your requirements. Your writing style should reflect the different needs of different stakeholders.

Is your audience primarily technical, such as software developers or systems engineers? Or does it include business stakeholders, customers, and regulatory auditors? Knowing your audience allows you to make informed decisions about the vocabulary and technical depth as well as how much background information to supply.  

Best Practice: Write for your primary audience but provide links to supporting material for secondary audiences. This ensures that developers get the precise information they need without being bogged down by context they already know, while other stakeholders can access the background details if necessary. 

2. Provide Relevant Information

Once you understand your audience, you must determine what each requirement will be used for. Is it intended to provide specific details for developers? Is it needed to secure buy-in from management?

Different types of requirements necessitate different levels of detail. High-level business requirements focus on the "what" and "why" from a strategic perspective, whereas lower-level functional specifications must detail the "how."

Best Practice: Consider perspectives and provide the most relevant information for that audience. Avoid subjective or vague terminology in favor of clear metrics and specific actions.

• QA Perspective: Requirements must be verifiable. They should clearly describe inputs and expected outputs so test cases can be written effectively.
• Development Perspective: Requirements must be feasible. They need to describe functionality that can be realistically implemented within the constraints of the system.

Examples  

SVG Poor Requirement	SVG Good Requirement
“The system shall provide quick response times to user requests.”	“The system shall provide quick response times to user requests.”
“As a WYSICORP customer, I need to save my order so that I can later save a copy, print, or email the list for other uses.”	“As a WYSICORP customer, I need to save, copy, print, and email my order so that I can edit it again, check a received shipment against a printed list, and send the list to a supplier.”
“The system must log errors when logins fail.”	“The system must add an error message to the server log when users attempt to login with an invalid username or password.”

3. Use Clear, Simple Language

Complexity is the enemy of execution. Useful requirements are clear, concise, and descriptive. Remember that human beings must read and interpret your documents.  

Best Practice: Avoid jargon, convoluted sentence structures, or ambiguous terms that obscure meaning. A developer shouldn’t have to re-read a requirement three times to understand it.

Example 

SVG Poor Wording	SVG Good Wording
“The system shall enforce the usage of a robust password protocol by disallowing any user password not consisting of, at minimum, eight alphanumeric characters, of which there must be, at minimum, one uppercase character and one numeric character.”	“User passwords must be at least eight characters long and contain at least one number and one uppercase letter.”

4. Find the Sweet Spot

One of the hardest parts of requirements engineering is determining how much detail you should supply. If a requirement is too short, it may be ambiguous. If it is too long, it becomes difficult to review, estimate, and test. You need to find the "sweet spot."

Best Practice: When determining how much information to include, consider:

• Project Complexity: Highly complex systems usually require more granular specifications.
• Methodology: Agile user stories are often less detailed than traditional Waterfall specifications.
• Regulatory Requirements: Industries like medical device manufacturing often mandate extensive documentation for audit trails.
• Team Geography: If your team is distributed globally, you cannot rely on hallway conversations to clarify ambiguity. In these cases, requirements must be explicit and self-contained to prevent misinterpretation across dispersed teams. 

5. Incorporate Visuals

Simple, clear, detailed text is not always the best means of communicating requirements with visual elements. Sometimes, a diagram, workflow chart, or wireframe can clarify a requirement instantly.

Visuals are particularly helpful for User Interface (UI) requirements. Describing the placement of a button in text is tedious and prone to error. Showing a mock-up clears up any uncertainty.

However, there is a risk. Visuals can become outdated quickly as the design evolves.

Best Practice: If you use visual aids:

• Clearly label them as "representative" if they are not final specifications.
• Establish a process to update diagrams when the requirements change.
• Ensure the text description remains the "source of truth" if the image becomes irrelevant. 

6. Be Consistent

Consistency reduces friction. If you switch between "The user shall..." and "The system must..." without a clear reason, you confuse the reader about priority and obligation.  

Requirements should follow a standard format and be grouped logically. This allows reviewers to easily scan the document and understand how different pieces fit together.

Best Practice: Structure Your Requirements:

• Templates: Use a standard template for writing requirements to ensure no critical information (e.g., priority, source, rationale) is missed.
• Terminology: Define a glossary of terms and stick to it. Do not use "user," "client," and "customer" interchangeably if they mean the same thing.
• Imperatives: Standardize your use of keywords. For example, use "MUST" for mandatory requirements and "SHOULD" for optional or desirable features (often following RFC 2119 standards). 

7. Establish Clear Ownership

In requirements engineering, unclear ownership leads to chaos. If a developer has a question, they need to know exactly who to ask. If a requirement needs to change because of a technical limitation, there must be a clear approval chain to ensure the change doesn't violate a business or regulatory goal.

Best Practice: maintain a traceability matrix or use an ALM tool that automatically tracks:

• The author of the requirement.
• The current status (Draft, Review, Approved).
• The history of changes (Who changed what, when, and why). 

8. Share the Status

Requirements are living documents. They move through a lifecycle: Draft -> Review -> Approved -> Implemented -> Verified.

If the status of a requirement is hidden in a spreadsheet on someone's hard drive, the rest of the team is left in the dark. Your project management process must communicate the real-time status of each requirement to the team.

Best Practice: Automate status updates. Using static documents (like Word or Excel) often leads to version control nightmares where developers work off outdated specs. A dynamic ALM solution ensures that everyone views the current status and can easily find any features that are still being defined. 

9. Listen To Feedback

The requirements engineering process does not end when the document is signed off. The ultimate test of a requirement is how the final product performs.

Best Practice: Conduct post-mortems after releases. Pay special attention to bugs reported by QA that were marked as "Not a Bug" or "Working as Designed" during development. These often indicate a disconnect between the requirement and the implementation. In these instances, the requirement was likely ambiguous or misunderstood. 

Poor vs. Good Requirements Writing: Two Examples

Below, we contrast two poorly written requirements with well-structured, verifiable requirements for both software and hardware domains.

Software Development Example

Scenario: A development team is building a secure login system for a web application. 

SVG Poor Requirement	SVG Good Requirement
"The system should be secure and allow the user to log in quickly without being too confusing."	"The User Authentication System must allow a registered user to access their account within 2.0 seconds of submitting valid credentials. The system must enforce a password complexity policy requiring a minimum of 12 characters, including at least one uppercase letter, one number, and one special character."
CRITIQUE    Ambiguous: What does “secure” mean in this context? HTTPS? 2FA? Biometrics? Subjective: “Quickly” is relative. Is 1 second quick? Is 10 seconds quick? Not Testable: “Without being too confusing” cannot be objectively tested by a QA engineer. Weak Verb: “Should” implies the requirement is optional.	WHY THIS IS BETTER    Specific: It defines exactly what constitutes a complex password. Measurable: The performance metric (2.0 seconds) is explicitly stated. Testable: A test script can easily verify if a 12-character password works and an 11-character password fails. Mandatory: Uses "must," indicating this is a constraint cannot be ignored.

Hardware Development Example

Scenario: Engineering battery performance for a new handheld IoT device. 

SVG Poor Requirement	SVG Good Requirement
"The device needs to have a really strong battery that lasts a long time so the user doesn't have to charge it often."	"The device must operate continuously for a minimum of 24 hours while transmitting data via Wi-Fi at 5-minute intervals, powered by a single internal rechargeable Li-ion battery. The battery must allow for a full recharge (0% to 100%) in under 90 minutes using the standard USB-C 5V/2A input."
CRITIQUE Vague: "Strong battery" is marketing language, not an engineering specification. Undefined Context: "Lasts a long time" depends entirely on usage. Does it last a long time while sleeping, or while processing heavy data? User-Dependent: "Often" is subjective to the user's habits.	WHY THIS IS BETTER Contextualized: It defines the operating conditions (transmitting data at 5-minute intervals). Quantified: "24 hours" and "90 minutes" are strict, measurable pass/fail criteria. Standardized: It specifies the charging interface (USB-C) and input power (5V/2A).

Requirements Best Practices Checklist

Use this checklist to validate your requirements before moving to development: 

• Is the requirement complete?
  Can the reader understand it without referencing external conversations?
• Is the requirement clear?
  Is it unambiguously worded? Do all stakeholders agree on the meaning?
• Is the requirement consistent?
  Does it conflict with other requirements? Is the terminology consistent with the glossary?
• Is the requirement verifiable?
  Can the QA team write a test case for it? Can it be verified via inspection or analysis?
• Is the requirement traceable?
  Does it have a unique identifier? Can it be linked to a business objective?
• Is the requirement design independent?
  Does it say what the system must do, rather than how it must do it (unless a specific constraint is required)? 

Final Thoughts 

Writing useful requirements is a skill that saves time, money, and headaches. By knowing your audience, being specific, using clear language, and maintaining consistency, you set your team up for success.

However, managing those requirements through a complex lifecycle, especially within a regulated industry, is where the real challenge lies. Manual processes cannot scale to meet modern compliance demands.

Perforce ALM automates traceability, manages risk, and ensures compliance through upstream and downstream traceability. With ALM, you get the visibility you need to deliver high-quality products on time. 

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