Part related to idempotency — how did it come about? Was it not formulated in the requirements?

Idempotency is a property of an operation where repeated execution with the same input does not change the result after the first time. In embedded systems, it often does not appear initially in the requirements but emerges during development when it is discovered that due to failures or repeated commands, the device may receive the same command multiple times.

For example, if a device receives a power-on command, and for some reason, the command is repeated, without idempotency, the device could switch to an undesired state or perform the action multiple times. To prevent this, developers implement logic that checks whether the command has already been executed and ignores subsequent calls.

Thus, idempotency arises as a response to practical issues of system reliability and robustness, even if it was not explicitly specified in the initial requirements.