Non-functional requirement template

A template for writing a non-functional requirement with four mandatory parts — property, value, conditions, method — and two useful ones: where the number came from, and when it is checked. Why a requirement missing any of the four cannot be checked is covered in the piece on testable non-functional requirements.

Form

NFR           <NFR-NN>  <property and object: “Search response time”>
Property      <what exactly is measured>
Value         <the boundary; for time — percentiles, not the average>
Conditions    <data volume, load, time, type of operation>
Method        <where, with what, from which data>
When          <on staging before release / in production from logs / a drill>
Who           <who checks, and whom they report a violation to>
Source        <current-version measurement / cost of downtime / comparables — assumption?>
Review        <when to come back to the number>

Examples

Performance.

NFR           NFR-03  Catalogue search response time
Property      time from request to server response
Value         95% of requests within 1 s, 99% within 3 s
Conditions    catalogue of 500k items, 200 concurrent users
Method        load test using a profile of a week of real queries
When          on staging before every release; in production — 24 h of logs
Who           load tester; a violation blocks the release
Source        current version measured: 95% — 1.4 s; target — no worse, and faster
Review        when the catalogue reaches 1M items

Availability and recovery. Two numbers set separately: how much data can be lost, and how fast the system must be back.

NFR           NFR-08  Recovery after database server failure
Property      data loss and recovery time
Value         loss — no more than 15 minutes of work;
              recovery — within 2 hours
Conditions    complete failure of the primary server during working hours
Method        drill: restore from backup onto a clean machine
When          once a quarter
Who           operations; report to the product owner
Source        assumption: an hour of downtime ≈ an hour of revenue; confirm with finance
Review        after the drill

Retention. A requirement that cannot be added retroactively.

NFR           NFR-12  Retention of the operator action log
Property      retention period and completeness of records
Value         every change to an order’s status and amount: who, when, was/now;
              kept for 3 years, then deleted
Conditions    all roles allowed to modify orders
Method        sample of 20 changes from last month — all present in the log
When          at acceptance and every six months
Who           analyst and security
Source        contractual obligations to customers
Review        when contract terms change

Notes on the fields

A non-functional requirement with “Method” and “When” filled in becomes an acceptance criterion by itself — there is no need to rewrite it in another format.