Edition 3 at DIS ballot, stage 40.20/ Planning date 12 September 2027, an estimate/ ISO/IEC/IEEE 29148:2018 applies today
ISO 29148 Revision CheckerThe requirements record, clause by clause, and the edition that follows it
5.2.6
ISO/IEC/IEEE 29148:2018
Concepts

Clause 5.2.6: Characteristics of a set of requirements

Current editionISO/IEC/IEEE 29148:2018, Clause 5.2.6Edition 3 at DIS ballotNo public change recorded

A set of requirements has its own five characteristics.

What clause 5.2.6 asks

A set of requirements has its own five characteristics. It is complete when it stands alone and contains no To Be Defined, To Be Specified or To Be Resolved clauses. It is consistent when its requirements are unique, do not conflict or overlap, use the same units and the same terms for the same thing. It is feasible when the whole set can be delivered within the entity constraints with acceptable risk, including affordability. It is comprehensible when a reader can see what is expected and how the set relates to the wider system. It can be validated when satisfying the set would actually meet the need within cost, schedule, technical, legal and regulatory limits.

Why it matters

The set characteristics catch what individual review misses: duplication, conflict, inconsistent units and unresolved placeholders. The TBx rule is strict at baseline: placeholders can exist while the set is being built, but the set is not complete until they are resolved. The clause also links completeness to requirements creep, because an unresolved set is where late change starts.

In the public record

No clause level change is public for this unit; the DIS keeps the title and scope, and the requirement text is not released.

What good looks like

Build a set-level review separate from the statement review. Check duplicates by capability, not by wording. Check units and terms with a glossary. Keep a TBx register with an owner and a resolution date, and do not call the set complete while any item is open.

Evidence an assessor asks for

The assessor will search the set for a TBx and ask who owns it. A closed TBx with no resolution is still open.

  • Set review record A review of the whole set for duplication, conflict, units and terminology
  • TBx register Each open To Be Defined, Specified or Resolved item, with an owner and a target date
  • Glossary The terms and units used by the set, with one meaning for each
  • Feasibility note The cost, schedule and technical case that the whole set can be delivered

Where it commonly fails

  • A set marked complete while three TBDs remain, because the deadline arrived
  • The same term used with two meanings in two subsystems
  • Each requirement is feasible on its own, but the set exceeds the budget

What to do before the revision

Run the set review after the statement review, never before. Use a duplicate detector on the capability, then a glossary check, then the TBx register. Record the result as a set-level gate.

Read across

← 5.2.5 Characteristics of individual requirements 5.2.7 Requirement language criteria →

Full register / Revision record

Source for clause 5.2.6: ISO/IEC/IEEE 29148:2018, Clause 5.2.6, retrieved 19 October 2026. The revision note rests on ISO page 94091. The requirement, evidence and gaps are written from our record. Every source.