Write Non-Functional Requirement

Use this skill to define constraints on how well the system performs (quality attributes).

Rules

• One Attribute: One quality per NFR (e.g., Security, Performance).
• Measurable: Must be objectively assessable.
• No Behavior: Do not define what the system does, but how it does it.
• Normative: Use SHALL.
• Traceable: Impacted FRs must be defined in the YAML frontmatter relationships: array.

Attributes (ISO 25010)

• Performance Efficiency
• Reliability / Availability
• Security
• Usability
• Maintainability
• Portability
• Scalability
• Compliance

Process

1. Select Attribute: Choose primary quality attribute.
2. Use Template:
   • Source: assets/nonfunctional-requirement-template.md
3. Define:
   • Statement: Atomic normative constraint.
   • Measurement: Metric, Target, Threshold, Method (required table).
   • Verification: objective, repeatable check of the table.
   • Impact: List affected FRs (FR-XXX).
4. Output: Save to correct location.
   • Single Repo: spec/non-functional/NFR-XXX-description.md
   • Multi-Repo: specs/<category>/<component>/spec/non-functional/NFR-XXX-description.md

Frontmatter (Required)

Every NFR file MUST contain the following YAML frontmatter:

---
id: NFR-XXX
title: "<Title>"
artifact_type: NFR
quality_attribute: performance_efficiency   # ISO 25010 enum (snake_case) — replaces the retired "## Quality Attribute" section
relationships:          # Required: Structured array of affected FRs
  - target: "ix://org/repo/FR-XXX"
    type: "constrains"
    cardinality: "1:N"
---

Body Shape (spec-artifacts-iso v0.2.0)

• REQUIRED (level 2): ## Statement, ## Measurement and Evaluation (table headers exactly Metric | Target | Threshold | Method, ≥1 row), ## Verification.
• OPTIONAL: ## Scope, ## Rationale, ## Acceptance Criteria, ## Dependencies. The Measurement table IS the acceptance-criteria equivalent for measurable NFRs; use the optional AC section only for policy NFRs whose compliance checks don't reduce to metrics.
• quality_attribute lives in FRONTMATTER (enum), not as a body section.