What is a single source of truth?
Every team says it wants a single source of truth. Here's what the phrase actually means for product work, and why copies keep creeping back.
Updated
Definition
A single source of truth is one place where a piece of information is kept and maintained, so everyone reads the same version instead of copies that drift apart.
What it is in practice
In product teams, the same facts get written down again and again: a milestone date in the roadmap slide, in the brief, in the tracker and in last week's update. Each copy starts accurate. Within a week, they disagree, and people spend time working out which one is right.
A single source of truth doesn't mean one tool for everything. It means each fact has one home, and every other place reads from it instead of storing its own copy. A roadmap that is built from the milestones themselves can't disagree with them. A status update that reads the work can't be out of date.
The test is simple: when something changes, how many places does someone have to edit? If the answer is more than one, you have copies.
An example from Pulse Analytics
In the Meridian Labs demo, the Pulse Analytics product brief mentions the Self-serve dashboards milestone. Instead of typing the date into the brief, the doc shows the milestone as a live chip. When the date changes, the brief, the roadmap and the product overview all show the new date, because they are reading the same record.
Common mistakes
- Declaring one tool the source of truth while status still gets copied into slides every week.
- Pasting dates and statuses into docs, where they start going stale immediately.
- Keeping several trackers "in sync" by hand.
- Confusing one tool with one source. The goal is one home per fact, wherever it lives.
How Ondule handles this
In Ondule, roadmaps, releases, docs and the canvas read the same objectives, milestones and epics, so a change made once shows everywhere.
Questions
- What is an example of a single source of truth?
- A milestone date kept on the milestone itself, with the roadmap, docs and updates reading it instead of copying it.
- Does a single source of truth mean using one tool?
- Not necessarily. It means each piece of information has one maintained home that everything else reads from.
- Why do copies keep coming back?
- Usually because the source is hard to share or read, so people paste the information somewhere more convenient.