The foundational principle behind most of BIM's process discipline: information about a project should exist in exactly one authoritative place, with everything else - drawings, schedules, reports - generated from it, rather than maintained as separate, parallel copies that inevitably drift out of sync. A schedule pulled live from the model is a single source of truth in action; a spreadsheet someone maintains by hand alongside the model is the opposite.

The CDE is the organizational mechanism that makes a single source of truth possible at the project level - a defined, agreed place where the current, correct version of every piece of information lives, so nobody is ever working from an outdated copy without realizing it.