Requirements & behavior · Requirements syntax
EARS
Give a textual requirement explicit context, trigger, and observable system response.
What it helps you do
Reduce ambiguity in behavioral requirements while keeping them readable to people who do not use formal logic.
Starting knowledge: No specialist knowledge is required.
- Identify the system that must respond.
- State the trigger or applicable state before the response.
- Specify an observable response and retain conditions and exceptions.
The problem it came from
Alistair Mavin and colleagues developed EARS while analyzing requirements for a jet-engine control system at Rolls-Royce. The notation was first published in 2009.
Its small set of patterns constrains requirement structure without introducing a general-purpose programming language. The creator’s guide is the primary reference.
Work through an example
When a former team member requests a team document, the workspace shall deny the new read request.
Scope: this requirement concerns new requests after revocation.
Open decision: how to handle in-flight reads and cached copies.- The trigger and response can be exercised in a scenario.
- The requirement distinguishes new requests from broader revocation behavior.
- The missing policy is recorded as a question.
Where it helps. Where it stops.
Use it when
- Turning a feature intention into reviewable behavior.
- A requirement uses “quickly,” “appropriately,” or an unclear actor.
Potential benefits
- An explicit trigger makes it easier to construct a scenario.
- A named response exposes missing acceptance details.
Limits and common mistakes
- Correct syntax can express the wrong policy.
- Timing limits, scope, and priorities still require real decisions; do not invent them to complete a sentence.
The prompt below asks for this structure. It does not guarantee accuracy, complete coverage, better learning, or conformance to a standard. Treat those outcomes as separate checks.
Practise the judgment
Try a choice, inspect a boundary, then explain a case yourself. Hints and answers are available whenever you need them.
Which requirement is most testable as written?
Hint
Look for a trigger and an observable result.
Explained answer
Best answer for this case: When an email is missing, the form shows an email-required error
The condition and visible response are explicit. The others require interpretation before a check can be written.
“The system responds quickly” has no agreed limit. What should the author do?
Hint
Writing a precise-looking number is not evidence of agreement.
Explained answer
Best answer for this case: Record the missing acceptance limit
The syntax cannot supply a stakeholder decision. Keep the gap visible.
Write a requirement for a duplicate confirmed workshop registration.
Hint
What resource must not be consumed twice?
Explained answer & self-review rubric
When a participant resubmits an already confirmed registration for the same workshop, the registration service shall return the existing confirmation without allocating another place.
- Identify the duplicate context
- Specify the response
- Preserve the capacity consequence
Take it into your own work
Manual template
Use this structure yourself, with a colleague, or in your preferred writing tool.
# Behavioral requirement
System:
Context or applicable state:
Trigger:
Required observable response:
Timing or limits (agreed):
Exceptions:
Open decisions:
Concrete examples:
Review the result
- Is the actor or system named?
- Can the trigger and response be observed?
- Are unresolved thresholds marked as unresolved?
Use this approach with your own AI tool
Help me apply EARS to the material below.
Reader and existing knowledge: [describe]
Task and desired outcome: [describe]
Use these principles: Identify the system that must respond.; State the trigger or applicable state before the response.; Specify an observable response and retain conditions and exceptions..
Preserve source facts, identifiers, quantities, conditions, exceptions, and uncertainty.
Separate supplied facts from assumptions. Ask for missing information instead of inventing it.
Explain your representation choices and provide a review checklist. Do not claim formal compliance or correctness from formatting alone.
Material: [paste only information you are permitted to share]Go to the source
History and the underlying approach are grounded in these references. Examples, prompts, and practice cases here are original educational adaptations. Edition-specific details should be checked against the referenced publication.
Last editorial review: 2026-10-24. An overview is not certification, and this guide is not a reproduction of a standard.