6.2 Functional suitability measures

What this heading covers

This is the characteristic most teams think they already measure, and the one where the population is most often wrong. Completeness needs a requirement set to be complete against. Correctness needs an expected result for every case. Appropriateness needs a task and a user, not a feature list. The draft separates the three into their own families, which is a warning against the single percentage of requirements met that many programmes report as functional quality. A product can meet every written requirement and still be functionally inappropriate for the task it is put to.

Record position: characteristic 1 of 9, carrying 3 of the 40 measure families in clause 6.

What the heading asks of a team

The common confusion

Completeness, correctness and appropriateness are often collapsed into a single percentage of requirements met. The draft keeps them apart because each fails for a different reason, and the single percentage hides two of the three.

The measure families in this characteristic

• 6.2.2 Functional completeness measures
• 6.2.3 Functional correctness measures
• 6.2.4 Functional appropriateness measures

What to put in place before publication

1. Assemble the requirement baseline the completeness measure will use, with an identifier for every requirement and its status.
2. Define the expected result for correctness at the level the product is tested, and record where the expectation came from.
3. Name the tasks and user groups the appropriateness question is about, because it cannot be answered without them.
4. Decide now how functional adaptability will be measured, and mark it as a local measure, since the draft has no family for it.
5. Put the three results side by side in the report rather than averaging them.

Where teams usually fall short

• One percentage of requirements met, presented as functional quality, with no correctness or appropriateness measure behind it.
• A baseline that was edited after testing, so completeness improves without any change to the product.

What happens next

Read the three family pages in order: completeness, correctness, appropriateness. The first two are the ones an acquirer will ask for; the third is the one that decides whether the product is any use.