# Single source of truth

> One agreed place where a fact is maintained, with other documents linking to it rather than keeping separate copies.

## What it means

The work meaning — one agreed place where a fact lives and everything else reads from it — next to the data-engineering meaning that shares the phrase. Everyday failures it prevents: the revenue figure in a deck, a model and an update disagreeing. How to set one up: name the source, link rather than copy, date it.

## A practical example

The board deck reads its monthly total from the same table as the finance chart instead of retyping the number.

## Put it into practice

- Name the concrete situation before applying the label. Single source of truth is useful only when it changes a choice, boundary or next action.
- Make the state visible: write the owner, time, source or stopping condition down instead of relying on memory.
- Review what happened. Keep the part that reduced ambiguity and change the part that added ceremony without helping the work.

## How it relates to Plexii

a Chart, Metrics and a Stat card read the rows of a Table and redraw when it changes (/help/widget-chart, /help/widgets-dashboard); duplicated widgets can stay in sync across desks (/help/widget-duplicate-sync). Link /blog/investor-update and /templates/monthly-investor-update.