In AEC industry with reference to information systems management, the single source of truth refers to Common Data Environment (CDE)

The single source of truth is a method of structuring information models and related CDE in such a way that every data element is stored exactly once.

Any possible links to this data element (perhaps in other areas of the CDE or even in distant federated databases) are by reference only.

Because all other locations of the data just refer to the primary “source of truth” location, updates to the data element in the primary location propagate to the entire system without the possibility of a duplicate value somewhere being forgotten.

[source:  Babylon software thesaurus, word ‘schema’ replaced by CDE]