The MPrin of technical debt incurred as a consequence of a platform component upgrade depends on how we incur the debt. If we incur the debt by installing the upgrade, and then performing only some of the work needed as a consequence of the upgrade, then the MPrin is the total cost of performing the work we deferred. If we incur the debt by deferring the upgrade, then the conventional definition of the MPrin is the cost of the upgrade plus the cost of any work necessitated by the upgrade, but not performed.
In this latter instance, MPrin can increase over time if some of the work performed in the environment of the obsolete platform component, but subsequent to deferring the upgrade, must later be repeated after the upgrade is ultimately installed. This situation can be even worse if the work performed in the environment of the obsolete platform component fails after the upgrade, but the maintainers do not recognize the reason for the failure. In that case, an investigative effort is required first, to determine the cause of the failure. These additional costs are actually part of the debt retirement effort for the debt incurred by deferring the upgrade, but they’re usually accounted for — mistakenly — as routine operational expense.
Available: here; Retrieved: November 21, 2017