EARS Authoring

EARS (Easy Approach to Requirements Syntax) pattern authoring for precise, unambiguous requirements.

When to Use This Skill

Keywords: EARS patterns, ubiquitous requirements, state-driven requirements, event-driven requirements, unwanted behavior, optional features, complex requirements, SHALL keyword, requirement syntax

Use this skill when:

• Writing new requirements using EARS syntax
• Converting informal requirements to EARS format
• Validating EARS pattern correctness
• Selecting the right EARS pattern for a requirement
• Understanding EARS anti-patterns

Quick Pattern Reference

Pattern	Keyword	Template
Ubiquitous	(none)	The <entity> SHALL <action>
State-Driven	WHILE	WHILE <condition>, the <entity> SHALL <action>
Event-Driven	WHEN	WHEN <trigger>, the <entity> SHALL <action>
Unwanted	IF...THEN	IF <condition>, THEN the <entity> SHALL <action>
Optional	WHERE	WHERE <feature>, the <entity> SHALL <action>
Complex	Multiple	Combination of patterns

Pattern Selection Decision Tree

Start here: When does this requirement apply?

1. Always applies (no conditions) → Use Ubiquitous: "The system SHALL..."

2. While in a specific state → Use State-Driven: "WHILE in maintenance mode, the system SHALL..."

3. When something happens (event/trigger) → Use Event-Driven: "WHEN user clicks submit, the system SHALL..."

4. To handle unwanted behavior (error/exception) → Use Unwanted: "IF authentication fails, THEN the system SHALL..."

5. Only when feature is enabled (optional/configurable) → Use Optional: "WHERE dark mode is enabled, the system SHALL..."

6. Multiple conditions apply → Use Complex: "WHILE active, WHEN timeout occurs, the system SHALL..."

Pattern Details

Ubiquitous Pattern

Use when: Requirement applies unconditionally, always active.

Template:

The <entity> SHALL <action>

Keywords: None required (no WHILE, WHEN, IF, WHERE)

Examples:

• "The system SHALL encrypt all data at rest"
• "The API SHALL respond in JSON format"
• "The application SHALL log all user actions"

Common Mistakes:

• Adding unnecessary conditions when behavior is universal
• Using "should" instead of "SHALL"

State-Driven Pattern

Use when: Behavior applies while system is in a particular state.

Template:

WHILE <condition>, the <entity> SHALL <action>

Keywords: WHILE (at start)

Examples:

• "WHILE in maintenance mode, the system SHALL display a banner"
• "WHILE the connection is active, the system SHALL send heartbeats"
• "WHILE the user is authenticated, the system SHALL show the dashboard"

Common Mistakes:

• Using WHEN instead of WHILE (WHEN = event, WHILE = state)
• Describing events, not states

Event-Driven Pattern

Use when: Action triggered by a specific event or user action.

Template:

WHEN <trigger>, the <entity> SHALL <action>

Keywords: WHEN (at start)

Examples:

• "WHEN a user submits the form, the system SHALL validate inputs"
• "WHEN an error occurs, the system SHALL log the details"
• "WHEN the session expires, the system SHALL redirect to login"

Common Mistakes:

• Using WHILE instead of WHEN (WHILE = state, WHEN = event)
• Describing states, not events

Unwanted Behavior Pattern

Use when: Handling exceptions, errors, or unwanted conditions.

Template:

IF <condition>, THEN the <entity> SHALL <action>

Keywords: IF...THEN (both required)

Examples:

• "IF authentication fails, THEN the system SHALL lock the account"
• "IF the database is unavailable, THEN the system SHALL queue requests"
• "IF input validation fails, THEN the system SHALL display error messages"

Common Mistakes:

• Using IF-THEN for normal behavior (use Event-Driven instead)
• Missing THEN keyword
• Using for positive conditions (reserve for negative/unwanted)

Optional Feature Pattern

Use when: Behavior depends on feature flag or configuration.

Template:

WHERE <feature/config>, the <entity> SHALL <action>

Keywords: WHERE (at start)

Examples:

• "WHERE dark mode is enabled, the system SHALL use dark theme"
• "WHERE audit logging is configured, the system SHALL log access"
• "WHERE two-factor authentication is enabled, the system SHALL require OTP"

Common Mistakes:

• Using IF instead of WHERE (IF = unwanted, WHERE = optional)
• Describing mandatory features as optional

Complex Pattern

Use when: Requirement combines multiple conditions from different patterns.

Template:

<Pattern1>, <Pattern2>, the <entity> SHALL <action>

Examples:

• "WHILE active, WHEN timeout occurs, the system SHALL reconnect"
• "WHILE in production mode, IF error occurs, THEN the system SHALL notify ops"
• "WHERE caching is enabled, WHEN data changes, the system SHALL invalidate cache"

Common Mistakes:

• Using Complex when a simpler pattern suffices
• Nesting conditions too deeply (max 2 recommended)

Writing Quality Requirements

The SHALL Keyword

Always use SHALL for requirements:

• ✅ "The system SHALL validate input"
• ❌ "The system should validate input"
• ❌ "The system must validate input"
• ❌ "The system will validate input"

Why: SHALL indicates mandatory behavior. Other words are ambiguous.

Active Voice

Always use active voice:

• ✅ "The system SHALL encrypt data"
• ❌ "Data shall be encrypted"
• ❌ "Encryption shall be performed"

Single Requirement Per Statement

One action per requirement:

• ✅ "The system SHALL validate input"
• ✅ "The system SHALL log validation errors"
• ❌ "The system SHALL validate input and log errors"

Testable Requirements

Requirements must be testable:

• ✅ "The system SHALL respond within 200ms"
• ❌ "The system SHALL respond quickly"
• ✅ "The system SHALL support 1000 concurrent users"
• ❌ "The system SHALL scale well"

Anti-Patterns to Avoid

Anti-Pattern	Problem	Fix
"should" instead of "SHALL"	Ambiguous obligation	Use "SHALL"
Passive voice	Unclear actor	Use active voice
Multiple requirements	Untestable compound	Split into separate
Implementation details	Specifies "how"	Focus on "what"
Vague terms	Not measurable	Add specific metrics
Wrong pattern keyword	Semantic confusion	Match pattern to behavior

Validation Checklist

Before finalizing an EARS requirement:

• Uses "SHALL" (not should/must/will)
• Uses active voice (entity does action)
• Single behavior per statement
• Testable with measurable criteria
• Pattern keyword matches behavior type
• No implementation details (what, not how)

Integration with Canonical Spec

EARS requirements map to canonical specification:

requirements:
  - id: "REQ-001"
    text: "WHEN a user submits the form, the system SHALL validate inputs"
    priority: must
    ears_type: event-driven  # Matches pattern used
    acceptance_criteria:
      - id: "AC-001"
        given: "a user on the form page"
        when: "the user clicks submit"
        then: "the system validates all inputs"

References

Detailed Documentation:

• Pattern Reference - Complete pattern syntax and rules
• Examples - Real-world examples per pattern

Related Skills:

• canonical-spec-format - Canonical specification structure
• spec-management - Specification workflow navigation
• requirements-quality - INVEST criteria and quality assessment

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Last Updated: 2025-12-24