Alistair Mavin and a team from Rolls-Royce PLC first introduced the Easy Approach to Requirements Syntax (EARS) at the Requirements Engineering (RE 09) conference in 2009. Since then, the EARS requirement syntax has become a go-to framework for simplifying how we write and organize software requirements.
In this article, we will explore what EARS requirement syntax is, why it’s important, and how it can significantly improve the clarity and quality of your software requirements. We’ll also address common challenges in requirements writing and show how EARS provides a systematic way to overcome them.
What Is a Requirement?
Before diving into EARS requirement syntax, it’s crucial to understand what a requirement is. In software development, a requirement refers to a statement that describes:
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Functional requirements (FRs)
- The actions or functions a system must perform.
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Non-functional requirements (NFRs)
- Known limitations or resource constraints.
- Desired performance or quality levels.
Example Functional Requirements
- A website must allow users to create an account and log in securely.
- A mobile app must enable users to purchase products using their credit card.
Example Non-Functional Requirements
- The website must handle high traffic volumes without downtime.
- The mobile app must be compatible with Android and iOS.
Common Challenges in Writing Requirements
Even though requirements are the foundation of successful software projects, many teams face challenges such as:
- Lack of formal training on effective requirement writing.
- Use of natural language without constraints, leading to ambiguity.
- Requirements not being clear, concise, or coherent.
- Missing triggers or important context.
- Incomplete logic within requirements.
- Copy-and-paste duplication leading to an increase in defective requirements.
Introducing EARS: Easy Approach to Requirements Syntax
The EARS requirement syntax was developed to simplify and standardize how requirements are written. Rather than wrestling with overly complex sentences or missing details, EARS provides a straightforward template that ensures each requirement is well-defined, easy to read, and consistently structured.
Five EARS Patterns
EARS differentiates requirements into five primary patterns:
Ubiquitous (Always Occurring)
Defines fundamental properties of the system.
Example: “The software shall be written in Python.”Event-Driven
Triggered only when a specific event occurs.
Example: “When the payment is received, then the app shall send a notification.”Unwanted Behaviors
Manages undesired occurrences such as errors, failures, or faults.
Example: “If the password is entered incorrectly, then the app shall display an error message.”State-Driven
Activated while the system is in a particular state.
Example: “When in Do Not Disturb mode, then the software shall silence incoming calls.”Optional Features
Applies only if a certain optional feature is present.
Example: “Where the DisplayPort is present, then the software shall allow users to select the maximum supported refresh rate.”
In some cases, requirements can also be complex, combining multiple triggers and conditions. For instance:
Complex Requirement Example
- “When the reverse gear button is pressed once, if the software detects that the gear is not engaged, then the software shall display a notification.”
Applying EARS Requirement Syntax to Ambiguous Requirements
One of the key benefits of EARS requirement syntax is its ability to transform vague, ambiguous requirements into clear, actionable statements. Consider this original requirement:
Original Requirement:
“The system shall break network connection.”
Rewritten Using EARS Requirement Syntax
“When the disconnect button is pressed, then the software shall break the network connection.”
By specifying the condition (“When the disconnect button is pressed”) and the desired action (“the software shall break the network connection”), we remove ambiguity and provide a clear trigger-action relationship.
Conclusion
The EARS requirement syntax offers a powerful yet easy-to-implement framework for writing clear, consistent software requirements. By adopting EARS, development teams can avoid common pitfalls—such as ambiguity, missing triggers, and incomplete logic—and ensure that their requirements are both understandable and verifiable.
Whether you’re working on a small application or a large-scale enterprise system, implementing the EARS requirement syntax can help streamline your requirements engineering process. This leads to better communication among team members, clearer project objectives, and ultimately, a more successful software solution.
Embrace EARS, and take the complexity out of writing requirements—so you can focus on building software that meets its goals and delights its users.
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