What is DRY principle personal knowledge management?

DRY principle personal knowledge management is a concept in personal epistemology: Each type of information should have one canonical location — avoid duplication.

Example: You keep your task list in three places: a project management app, a notes document, and a paper notebook on your desk. On Monday, you complete a task and check it off in the project management app. On Tuesday, your colleague asks about it and you glance at the paper notebook — where it still appears undone. You tell her it is still in progress. On Wednesday, during a planning meeting, someone pulls up the notes document, which shows the task as active with an outdated deadline. Three copies of the same information, three different states, two miscommunications, and one planning decision made with stale data. Now compare: you designate the project management app as the single source of truth for all tasks. The paper notebook becomes a scratch pad for capturing during the day — items get transferred to the app during your evening sweep, then crossed off the paper. The notes document references the app for task status rather than maintaining its own copy. One canonical location. One current state. Zero drift. The fifteen seconds it takes to check the authoritative source replace the fifteen minutes spent reconciling conflicting versions.

This concept is part of Phase 46 (Tool Mastery) in the How to Think curriculum, which builds the epistemic infrastructure for tool mastery.