DTM.9:5.4 - Memory can outlast the condition that formed it

Suppose a receiving team keeps restricting an exchange format because earlier versions caused failures. The present format and conversion method have changed, but the restriction uses accumulated historical evidence.

The response state must then distinguish current compatibility from retained evidence. A comparison of current verified exchange and the rule’s update behavior can reveal whether the restriction still protects the intended work. A memory-free relation to current usage would miss that question.

For a small constructed case, let m be a retained warning score. The rule holds the format when m≥0.4, starts at m_0=0.8, and updates after an authorized exchange test by m_next=0.8m+0.2e, where e=1 for a failed test and 0 for a successful one. Four successful tests give scores 0.64, 0.512, 0.4096 and 0.32768. The rule therefore still holds the format after the first three tests and releases it after the fourth, although the latest observed outcome is the same throughout.

A rule based only on the latest outcome would release it after the first success. Neither rule is justified by this arithmetic alone: the subject engineering method must establish which exchanges were tested and what evidence warrants admission. If the restriction also prevents every new test and the score has no other update, m remains 0.8 and the restriction sustains its own lack of new evidence.

The subject control and learning methods define how evidence is updated.