A recurring question among organisations implementing PRINCE2 alongside engineering or product development frameworks: if detailed functional and user requirement specifications already exist, do we still need PRINCE2 Product Descriptions? The short answer is no — detailed requirement documents don't eliminate the need for Product Descriptions, though they may reduce some of their content.
What Design Input Covers
If detailed design input — functional requirements, user stories, technical specifications — exists for a product, there is no need to duplicate these detailed requirements in the Product Description's quality criteria section. You can simply reference the requirement document as the quality standard.
What Product Descriptions Cover That Requirements Don't
Product Descriptions cover more than requirements alone. Even when separate requirement documents exist, Product Descriptions must still address:
- Quality methods — how the product will be reviewed, tested, or inspected before acceptance
- Quality tolerances — what level of deviation from the specification is acceptable
- Responsible parties — who will produce the product, who will review it, and who will accept it
- Derivation — what inputs the product is derived from
The Staging Argument
Design input documents typically describe the final desired product — not the intermediate deliverables produced at each project stage. A project delivering a software system in three stages (prototype, release candidate, final software) needs three distinct Product Descriptions. Each must clarify what quality level is expected at that specific stage — not just what the final system should look like.
This is the most compelling reason why requirement documents cannot fully replace Product Descriptions: they don't reflect how the product evolves through the project lifecycle.