Maintenance Knowledge

Seventy percent of all software engineering labor is devoted not to building new things but to keeping existing ones running. David Edgerton's use-centered history of technology reveals that this maintenance majority is not an anomaly but the structural norm across every technological domain: ten maintenance workers for every combat soldier in the Second World War, the bicycle mechanic as the unsung engine of healthcare delivery in the developing world, the railroad worker who kept the infrastructure of industrialization running long after the era of locomotive invention had ended. Maintenance knowledge is the cognitive resource that makes the maintenance majority possible—and it is the resource that large language models handle least well. It is not the knowledge that lives in documentation, which describes the system as it is supposed to work. It is the knowledge of the gap between specification and reality: the understanding of why a particular implementation was