Revision cloud

A drawing revision without clouds is a puzzle: something changed, and every reader must diff the sheet by eye to find it. Clouding is the courtesy and the control that prevents this — each changed region outlined, tagged with the revision marker, and described in the revision history block, so reviewers review the change rather than re-reviewing the drawing, and the field sees precisely what moved.

The convention's failures are its two abuses. The silent edit — a change made without a cloud — defeats the entire mechanism, and is rightly treated as a documentation offence rather than an oversight, because downstream users legitimately rely on unclouded areas being unchanged. The stale cloud — markers surviving from previous revisions — degrades the signal more gently, until sheets carry archaeological layers of clouds and readers stop trusting any of them. Cloud discipline is small, mechanical and disproportionately load-bearing, like most of revision control.