6.9 Flexibility measures

What this heading covers

The rename is not cosmetic. Portability was about moving a product to another environment. Flexibility is about how well the product adapts to changed requirements, changed scale and changed surroundings, and how easily it can be installed or replaced. Adaptability is about effectiveness and efficiency in a new environment. Scalability is about behaviour as load or size grows. Installability is about installing and uninstalling in a stated environment. Replaceability is about substituting the product for another in a stated context. The four families need different evidence: a migration test, a load test, an installation record, and a replacement scenario.

Record position: characteristic 8 of 9, carrying 4 of the 40 measure families in clause 6.

What the heading asks of a team

The common confusion

Flexibility is often treated as the old portability heading renamed. It adds scalability and widens adaptability, and a measure library carried over from portability will miss both.

The measure families in this characteristic

• 6.9.2 Adaptability measures
• 6.9.3 Scalability measures
• 6.9.4 Installability measures
• 6.9.5 Replaceability measures

What to put in place before publication

1. List the environments the adaptability measure covers, and the changes that count as a new environment.
2. Define the load or size axis for scalability, and the property that must stay acceptable as it grows.
3. Record an installation and an uninstallation on a clean environment, with time, steps and failures.
4. Name the product being replaced for the replaceability measure, and the context of the replacement.
5. Re-index any portability measures from the older model into the four families.

Where teams usually fall short

• Portability measures renamed to flexibility without adding scalability or replaceability evidence.
• An installation result from a machine that already had the dependencies installed.

What happens next

Read adaptability with replaceability, because both are about change in context, and scalability with the performance efficiency families, because the load axis is shared.