Originally written in French. Translated by AI — the meaning has been preserved, not the prose.
Short definition
An artifact designated as prevailing in case of disagreement between several representations of the same object, and from which the others are rebuilt or corrected.
Full definition
The phrase comes from information systems, where single source of truth designates the unique location where a datum is stored, the other locations holding only derived copies. The sense is strict there: uniqueness is a property of the architecture, guaranteed by the system.
In the articles on this blog, the term is used for artifacts and not for data, and uniqueness there is a choice of organization, not a technical guarantee. Nothing prevents a specification from contradicting the repository; designating the repository as the source of truth only says what will be done with the contradiction — correct the specification, never the reverse.
Two distinct properties are often conflated under this term. Prevailing is a rank: you know who is right. Serving as a source is a capacity: you know how to extract the other artifacts from it. An object can have the rank without the capacity — that was the situation of code as long as it stayed illegible to those who produced the documents.
Usage in the field
Used to settle a conflict between two artifacts without bringing their authors together, and to inform the direction of manufacture of a chain of product documents.
Synonyms and variants
"What prevails", "the reference", "single source of truth" in its original usage.
Not to be confused with
- Deliverable — Deliverable — a production shaped for a recipient, oriented by construction. A source of truth isn't oriented towards an audience; one and the same object can however be both, which is the case with code.
- Intermediate artifact — Intermediate artifact — a document produced to circulate information inside the organization, perishable and with no external recipient. It derives from a source of truth, it is never one.
- Feature flag — Feature flag — a switch written into the code and set outside it, whose state decides which of several behaviours runs. It doesn't compete with the source of truth: it is what prevents it from settling alone what a given customer observes.
- Archive — the preservation of what has been. The source of truth states the current state; the archive states a past state and doesn't claim to prevail on the present.
Examples
"Code is no longer only the final deliverable: it becomes the central element, the source of truth around which the product's other artifacts orbit and from which they are rebuilt."
Ambiguities / debates
The word "truth" suggests an exhaustiveness that doesn't exist. The repository prevails on what the product does and says nothing about what was intended or what was ruled out. An organization can therefore have several sources of truth without contradiction, if each reigns over a different question — which then strips the term of its original uniqueness.